Change the default value of --network-allow-private-ips to false for mainnet and fuji

[StephenButtolph]

Why this should be merged

It's generally unexpected behavior that avalanchego may attempt to connect to private IPs when run with the default configurations.

How this works

Because it is fairly common for nodes to need to connect to private IPs with non-production networks, this doesn't change the default value of --network-allow-private-ips for non-production networks. However, for mainnet and fuji the default value will be false.

How this was tested

Running on mainnet - this PR blocks a large number of connection dial attempts:

[07-27|13:36:56.025] VERBO network/network.go:1135 skipping connection dial {"reason": "outbound connections to private IPs are prohibited", "nodeID": "NodeID-LBA1YYYBbxwYMMAA9odGhR69d9SCbyq8v", "peerIP": "10.6.4.10", "delay": "1.857536142s"}
[07-27|13:36:56.161] VERBO network/network.go:1135 skipping connection dial {"reason": "outbound connections to private IPs are prohibited", "nodeID": "NodeID-Hbf2ZY1Zs1s8KMp3rA1zK36N7zt5fSLkz", "peerIP": "10.8.11.6", "delay": "1.150304756s"}
[07-27|13:36:56.166] VERBO network/network.go:1135 skipping connection dial {"reason": "outbound connections to private IPs are prohibited", "nodeID": "NodeID-AdCK93Gj4MnPU5Qj1tzRH166uiVBGzg7w", "peerIP": "10.70.2.1", "delay": "1.17332004s"}
[07-27|13:36:56.198] VERBO network/network.go:1135 skipping connection dial {"reason": "outbound connections to private IPs are prohibited", "nodeID": "NodeID-6S8zAjmFJ4JdZwPURyFGp8Q8tqQ5NcEbX", "peerIP": "172.17.112.56", "delay": "1.760768527s"}
[07-27|13:36:56.215] VERBO network/network.go:1135 skipping connection dial {"reason": "outbound connections to private IPs are prohibited", "nodeID": "NodeID-DJbw4TrSRu9uovTKqo6w12axPLHWHsjJD", "peerIP": "10.6.4.11", "delay": "1.465906138s"}
[07-27|13:36:56.215] VERBO network/network.go:1135 skipping connection dial {"reason": "outbound connections to private IPs are prohibited", "nodeID": "NodeID-Aua1pVxQsWLvTTf8bNVw2ZCA2NfogNqiE", "peerIP": "10.0.0.246", "delay": "1.89626065s"}
[07-27|13:36:56.246] VERBO network/network.go:1135 skipping connection dial {"reason": "outbound connections to private IPs are prohibited", "nodeID": "NodeID-6w8NN8PeYXnpxojbo73BUUXq6tDmV6hzr", "peerIP": "10.3.65.12", "delay": "1.129021199s"}
[07-27|13:36:56.246] VERBO network/network.go:1135 skipping connection dial {"reason": "outbound connections to private IPs are prohibited", "nodeID": "NodeID-D7JFYevRv4N7LXa8ihCwdzVtc5szT9Q7j", "peerIP": "10.20.4.5", "delay": "1.462733755s"}
[07-27|13:36:56.304] VERBO network/network.go:1135 skipping connection dial {"reason": "outbound connections to private IPs are prohibited", "nodeID": "NodeID-FF2Szx54cN5iys83j9H5xaEqHiz3RipkG", "peerIP": "10.20.3.5", "delay": "1.807390667s"}
[07-27|13:36:56.362] VERBO network/network.go:1135 skipping connection dial {"reason": "outbound connections to private IPs are prohibited", "nodeID": "NodeID-HWwYYkiTKnXgYycNN5gXQfxhhA8TZdBvs", "peerIP": "10.6.0.13", "delay": "1.868898153s"}
[07-27|13:36:56.579] VERBO network/network.go:1135 skipping connection dial {"reason": "outbound connections to private IPs are prohibited", "nodeID": "NodeID-AU27Fz35YmQuM6d2pM9HsvLtgwGT5xwnd", "peerIP": "172.18.0.3", "delay": "1.105249361s"}
[07-27|13:36:56.582] VERBO network/network.go:1135 skipping connection dial {"reason": "outbound connections to private IPs are prohibited", "nodeID": "NodeID-L9HsJPQ9TF5aXjdx3KnQrh1eWaHJaNXNj", "peerIP": "10.121.0.6", "delay": "1.348036315s"}
[07-27|13:36:56.615] VERBO network/network.go:1135 skipping connection dial {"reason": "outbound connections to private IPs are prohibited", "nodeID": "NodeID-4kRVv9q9bLrAVCdpgVXJfEBEUXSGkobMU", "peerIP": "172.18.0.3", "delay": "1.895168099s"}
[07-27|13:36:56.874] VERBO network/network.go:1135 skipping connection dial {"reason": "outbound connections to private IPs are prohibited", "nodeID": "NodeID-LG2NYC4RxxzCG4zFGWoAwSo4U8mjMux1f", "peerIP": "10.20.1.4", "delay": "1.514356098s"}
[07-27|13:36:56.952] VERBO network/network.go:1135 skipping connection dial {"reason": "outbound connections to private IPs are prohibited", "nodeID": "NodeID-7843EeyboY1mZSmdzjqdJodxHycNn7Kv2", "peerIP": "10.0.132.31", "delay": "1.279405893s"}
[07-27|13:36:57.026] VERBO network/network.go:1135 skipping connection dial {"reason": "outbound connections to private IPs are prohibited", "nodeID": "NodeID-JDS6pq6tZxZxePaDc77TvrmNnY5HBUNX4", "peerIP": "192.168.1.70", "delay": "1.650950491s"}
[07-27|13:36:57.117] VERBO network/network.go:1135 skipping connection dial {"reason": "outbound connections to private IPs are prohibited", "nodeID": "NodeID-KeyQeQwf1D4bzdcHVP34xXXWhJzFjVTSj", "peerIP": "172.31.45.225", "delay": "1.524901703s"}
[07-27|13:36:57.143] VERBO network/network.go:1135 skipping connection dial {"reason": "outbound connections to private IPs are prohibited", "nodeID": "NodeID-DvwWC5ed3j5iG6e4Y5yxAUacPkXvrxLFT", "peerIP": "10.6.0.12", "delay": "1.9147983s"}
[07-27|13:36:57.183] VERBO network/network.go:1135 skipping connection dial {"reason": "outbound connections to private IPs are prohibited", "nodeID": "NodeID-2eBu8RjbvCFTZMcxu1oh2oKtfHT7V4zyM", "peerIP": "10.21.10.140", "delay": "1.991633748s"}
[07-27|13:36:57.281] VERBO network/network.go:1135 skipping connection dial {"reason": "outbound connections to private IPs are prohibited", "nodeID": "NodeID-EoNXC39QyT1eHFPXb5PgvDNigBN8tMeCC", "peerIP": "172.18.0.6", "delay": "1.487049639s"}
[07-27|13:36:57.313] VERBO network/network.go:1135 skipping connection dial {"reason": "outbound connections to private IPs are prohibited", "nodeID": "NodeID-Hbf2ZY1Zs1s8KMp3rA1zK36N7zt5fSLkz", "peerIP": "10.8.11.6", "delay": "1.163580698s"}
[07-27|13:36:57.339] VERBO network/network.go:1135 skipping connection dial {"reason": "outbound connections to private IPs are prohibited", "nodeID": "NodeID-AdCK93Gj4MnPU5Qj1tzRH166uiVBGzg7w", "peerIP": "10.70.2.1", "delay": "1.663089539s"}
[07-27|13:36:57.376] VERBO network/network.go:1135 skipping connection dial {"reason": "outbound connections to private IPs are prohibited", "nodeID": "NodeID-6w8NN8PeYXnpxojbo73BUUXq6tDmV6hzr", "peerIP": "10.3.65.12", "delay": "1.621173601s"}
[07-27|13:36:57.409] VERBO network/network.go:1135 skipping connection dial {"reason": "outbound connections to private IPs are prohibited", "nodeID": "NodeID-EbqMEDUpxHXexLzcBabL696xQp2QEWWa5", "peerIP": "192.168.1.247", "delay": "1.778510485s"}
[07-27|13:36:57.418] VERBO network/network.go:1135 skipping connection dial {"reason": "outbound connections to private IPs are prohibited", "nodeID": "NodeID-HkEQ2sJogxEps4tmqFRDuVG9hyfxe8vMg", "peerIP": "10.0.141.95", "delay": "1.304702368s"}

(the list goes on, but this was just the first few I cared to see)