[API-1092] Convert `Config` classes to public API

[mdumandag]

These were converted into private classes during the 4.0 migration, as we were only supporting keyword arguments for the client configuration.

However, that led to a poor user experience, as we had to use **kwargs, instead of listing all the configuration elements in the client constructor. (IDEs become painfully slow once we list all keyword arguments, as there are too many of them)

The solution to this problem is to make the Config classes public API and make the client able to use it directly.

config = Config()
config.cluster_name = "dev2"

client = HazelcastClient(config)

We provide full type hints for config elements.

[codecov-commenter]

Codecov Report

Merging #521 (3ac182c) into master (975bb48) will increase coverage by 0.02%. The diff coverage is 99.22%.

@@            Coverage Diff             @@
##           master     #521      +/-   ##
==========================================
+ Coverage   96.46%   96.49%   +0.02%     
==========================================
  Files         349      357       +8     
  Lines       19821    20510     +689     
==========================================
+ Hits        19121    19791     +670     
- Misses        700      719      +19     

Impacted Files	Coverage Δ
hazelcast/config.py	99.50% <99.20%> (+0.29%)	:arrow_up:
hazelcast/client.py	99.57% <100.00%> (ø)
hazelcast/proxy/flake_id_generator.py	94.21% <100.00%> (ø)
hazelcast/proxy/reliable_topic.py	94.60% <100.00%> (ø)
hazelcast/reactor.py	87.82% <100.00%> (ø)
hazelcast/serialization/service.py	93.00% <100.00%> (ø)
hazelcast/statistics.py	87.64% <0.00%> (-0.57%)	:arrow_down:
hazelcast/proxy/multi_map.py	99.21% <0.00%> (-0.35%)	:arrow_down:
hazelcast/protocol/builtin.py	94.35% <0.00%> (-0.12%)	:arrow_down:
hazelcast/proxy/cp/__init__.py	97.77% <0.00%> (ø)
... and 9 more

:mega: We’re building smart automated test selection to slash your CI/CD build times. Learn more

[mdumandag]

@yuce can you force-merge this? I can't merge it because of the merge checks (they should be checking for ... ubuntu-20.04 but they are checking for ...ubuntu-latest in the name)