[API-582] Implement external smart client discovery

[mdumandag]

This PR implements the client-side support for the external smart
client discovery. With this PR, the Python client will be able
to use public addresses reported by the cluster members even
if the client and the cluster are in different networks.

To use it, one has to enable use_public_addresses option by setting
it to True, and passing at least one public address of the cluster
members to the cluster_members config. Client will initiate the
cluster connection using the provided public address, and will
discover the rest of the cluster using the public addresses reported
by them.

Protocol PR: hazelcast/hazelcast-client-protocol#394

[mdumandag]

Ali did the tests on Kubernetes on GKE with this branch, and the tests are passed.

Here is the link to his verification: https://github.com/alisengul53/GHActionTestRepo/runs/3542770380?check_suite_focus=true

[srknzl]

I started to review tests. Just wanted to send the reviews so far..

[yuce]

@mdumandag The Java client property that enables this feature is hazelcast.discovery.public.ip.enabled: https://hazelcast.atlassian.net/wiki/spaces/IMDG/pages/2689663054/External+Smart+Client+discovery+via+LoadBalancer+TDD I've also used config.Cluster.Discovery.UsePublicIP in the Go client. So, would it make sense to use something similar in the Python client as well?

[mdumandag]

@yuce I changed it to use_public_ip to match with others. WDYT?

At first, I used use_public_addresses because it sounded better to me but I really don't have any strong opinions about it.

[codecov-commenter]

Codecov Report

Merging #468 (e22a08e) into master (0d1cc31) will decrease coverage by 0.10%.
The diff coverage is 89.39%.

@@            Coverage Diff             @@
##           master     #468      +/-   ##
==========================================
- Coverage   94.96%   94.86%   -0.11%     
==========================================
  Files         345      345              
  Lines       17633    17685      +52     
==========================================
+ Hits        16745    16776      +31     
- Misses        888      909      +21     

Impacted Files	Coverage Δ
hazelcast/client.py	99.54% <ø> (ø)
hazelcast/protocol/__init__.py	94.73% <ø> (-0.27%)	⬇️
hazelcast/core.py	92.52% <85.71%> (-1.96%)	⬇️
hazelcast/cluster.py	90.44% <87.50%> (-0.14%)	⬇️
hazelcast/connection.py	91.88% <90.90%> (-0.77%)	⬇️
hazelcast/config.py	99.38% <100.00%> (+<0.01%)	⬆️
.../protocol/codec/custom/endpoint_qualifier_codec.py	73.07% <100.00%> (ø)
hazelcast/proxy/reliable_topic.py	95.40% <100.00%> (+0.01%)	⬆️
...otocol/codec/client_authentication_custom_codec.py	50.00% <0.00%> (-23.81%)	⬇️
hazelcast/reactor.py	81.79% <0.00%> (-8.26%)	⬇️
... and 5 more

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[srknzl]

I left one last additional comment in one of the previous review comments. Thanks for your patience and changes.

[yuce]

@mdumandag Thanks. I agree that address would be better. Not sure why the core/Java client property uses ip...