Adds credentials and custom authentication support

[yuce]

• Enables credentials and custom authentication.
• Adds creds_username, creds_password and token_provider configuration.
• Adds TokenProvider class, which is the base class for custom authentication classes.
• Adds BasicTokenProvider class for token-based authentication.
• Authentication docs, sample code and tests.

[yuce]

@mdumandag This one should be good to review.

[mdumandag]

I am OK with the code now. I will approve once the tests on Jenkins pass

[codecov-commenter]

Codecov Report

Merging #446 (b43455a) into master (4753b54) will increase coverage by 8.12%.
The diff coverage is 73.62%.

@@            Coverage Diff             @@
##           master     #446      +/-   ##
==========================================
+ Coverage   86.06%   94.19%   +8.12%     
==========================================
  Files         340      343       +3     
  Lines       17938    17440     -498     
==========================================
+ Hits        15438    16427     +989     
+ Misses       2500     1013    -1487     

Impacted Files	Coverage Δ
hazelcast/client.py	99.54% <ø> (+23.02%)	⬆️
...otocol/codec/client_authentication_custom_codec.py	50.00% <50.00%> (ø)
hazelcast/connection.py	91.02% <60.00%> (+8.29%)	⬆️
hazelcast/security/token_provider.py	92.30% <92.30%> (ø)
hazelcast/config.py	99.37% <100.00%> (+5.54%)	⬆️
hazelcast/security/__init__.py	100.00% <100.00%> (ø)
hazelcast/reactor.py	79.56% <0.00%> (-4.65%)	⬇️
... and 55 more

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