## Description 

before this PR, FN config is required to make sui NS work, this PR added
default mainnet sui ns config so that
- without extra setup, sui ns on mainnet should just work
- if RPC provider wants to override with custom ones, they still can
- on other *nets, overriding is still required.

## Test Plan 

Test on testnet with & without overriding.

---
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### Type of Change (Check all that apply)

- [ ] protocol change
- [ ] user-visible impact
- [ ] breaking change for a client SDKs
- [ ] breaking change for FNs (FN binary must upgrade)
- [ ] breaking change for validators or node operators (must upgrade
binaries)
- [ ] breaking change for on-chain data layout
- [ ] necessitate either a data wipe or data migration

### Release notes