Prepare 4.0.0 release

[kp-cat]

4.0.0

New features and improvements:

• Add support for the new Config JSON v6 format: update the config model and implement new features in setting evaluation logic.
• Overhaul setting evaluation-related logging and make it consistent across SDKs.
• The User's custom dictionary also allows attribute values other than String values.
• Upgrade to Elixir 1.16

Breaking changes:

• The config JSON v5 format is no longer accepted by flag overrides. If you use this feature, you will need to convert your override JSON file(s) to the v6 format. You can do this using the config-json convert v5-to-v6 command of the ConfigCat CLI tool.
• Rename the matched_evaluation_percentage_rule property to matched_targeting_rule and the matched_evaluation_rule property to matched_percentage_option in EvaluationDetails.
• Raise ArgumentError "SDK Key is invalid." when the SDK key passed to ConfigCat.Client is in an invalid format (unless the client is set up to use local-only flag override behaviour).

Requirement checklist (only if applicable)

• I have covered the applied changes with automated tests.
• I have executed the full automated test set against my changes.
• I have validated my changes against all supported platform versions.
• I have read and accepted the contribution agreement.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (b4110dd) 93.76% compared to head (7191ac2) 93.76%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #135   +/-   ##
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  Coverage   93.76%   93.76%           
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  Files          50       50           
  Lines        1315     1315           
=======================================
  Hits         1233     1233           
  Misses         82       82           

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