optimize: Extract datasource proxy metadata

[jsbxyyx]

• I have registered the PR changes.

Ⅰ. Describe what this PR did

Ⅱ. Does this pull request fix one issue?

fixes: #6721

Ⅲ. Why don't you add test cases (unit test/integration test)?

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

[codecov]

Codecov Report

Attention: Patch coverage is 70.70707% with 29 lines in your changes missing coverage. Please review.

Project coverage is 50.78%. Comparing base (d0f8c6f) to head (11213ab).

Files	Patch %	Lines
...asource/metadata/MySQLDataSourceProxyMetadata.java	43.90%	19 Missing and 4 partials ⚠️
...rg/apache/seata/rm/datasource/DataSourceProxy.java	71.42%	1 Missing and 1 partial ⚠️
...atasource/SeataDataSourceProxyMetadataFactory.java	83.33%	1 Missing and 1 partial ⚠️
.../rm/datasource/exec/mysql/MySQLInsertExecutor.java	88.88%	0 Missing and 1 partial ⚠️
...ource/metadata/DefaultDataSourceProxyMetadata.java	83.33%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x    #6722      +/-   ##
============================================
+ Coverage     50.24%   50.78%   +0.53%     
- Complexity     5854     5919      +65     
============================================
  Files          1058     1062       +4     
  Lines         36707    36725      +18     
  Branches       4364     4365       +1     
============================================
+ Hits          18442    18649     +207     
+ Misses        16431    16186     -245     
- Partials       1834     1890      +56     

Files	Coverage Δ
...datasource/exec/mysql/MySQLUpdateJoinExecutor.java	78.48% <100.00%> (ø)
...urce/metadata/AbstractDataSourceProxyMetadata.java	100.00% <100.00%> (ø)
.../rm/datasource/undo/mysql/MySQLUndoLogManager.java	30.00% <100.00%> (ø)
.../rm/datasource/exec/mysql/MySQLInsertExecutor.java	72.41% <88.88%> (-2.33%)	⬇️
...ource/metadata/DefaultDataSourceProxyMetadata.java	83.33% <83.33%> (ø)
...rg/apache/seata/rm/datasource/DataSourceProxy.java	79.84% <71.42%> (+10.27%)	⬆️
...atasource/SeataDataSourceProxyMetadataFactory.java	83.33% <83.33%> (ø)
...asource/metadata/MySQLDataSourceProxyMetadata.java	43.90% <43.90%> (ø)

... and 40 files with indirect coverage changes