refactor(serializer): remove contract

[flc1125]

No description provided.

[what-the-diff]

PR Summary

• Package Addition and File Structure Changes in go-kratos-components
  The github.com/go-packagist/go-kratos-components/serializer/json package has been updated with architectural changes. This includes renaming the serializer/json.go file to serializer/json/json.go, test files have been updated accordingly with json_test.go now residing inside the json folder.

• Update in Import Statement in Cache
  In the cache/redis/store.go file, import references have been updated resulting in the serializerContract being replaced by serializer. Also, a new variable json.Serializer has been introduced to the serializer struct.

• Renaming and Repointing of Variables in JSON Serializer
  The file serializer/json/json.go has witnessed a package name change from serializer to json. A notable renaming occurred with the global variable JsonSerializer updated to Serializer, pointing now to an instance of jsonSerializer.

• Test Function Update in JSON Serializer
  Changes in the serializer/json_test.go move the fetching of package serializer to serializer/json and modifying the test function name to TestSerializer. This function now uses the instance json.Serializer.

• Renaming of Serializable Contract
  The file contract/serializable.go is renamed to serializer/serializable.go with the changing of the package name from contract to serializer. Additionally, enhanced documentation has been provided for Serialize and Unserialize methods with added comments.

Note: The summaries above are deduced from the git diff and might not provide a full context around the changes.

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (7f2130f) 74.42% compared to head (508cc6f) 75.00%.

Files	Patch %	Lines
cache/redis/store.go	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #33      +/-   ##
==========================================
+ Coverage   74.42%   75.00%   +0.57%     
==========================================
  Files          22       22              
  Lines         610      608       -2     
==========================================
+ Hits          454      456       +2     
+ Misses        139      135       -4     
  Partials       17       17              

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