bugfix : upgrade vulnerable MySQL Connector/J references from distribution

[LegendPei]

• I have read the CONTRIBUTING.md guidelines.
• I have registered the PR changes.

Ⅰ. Describe what this PR did

This PR upgrade the vulnerable MySQL Connector/J references from Seata's dependency and distribution packaging configuration.

Main changes:

• Replace the managed MySQL Connector/J dependency from mysql:mysql-connector-java to com.mysql:mysql-connector-j.
• Remove the release/image packaging logic that copied MySQL driver jars into the Seata server distribution.
• Remove obsolete MySQL driver version properties used only by the removed copy strategy.
• Update test-scoped MySQL Connector/J usages to the new coordinates.
• Update affected test imports from legacy MySQL 5 internal classes to MySQL Connector/J 8 classes.
• Update NOTICE and changelog entries.

This keeps the change scoped to the GHSA/CVE cleanup and aligns with the point that the distributed binary package should not have a hard dependency on the MySQL driver.

Ⅱ. Does this pull request fix one issue?

fixes #8101

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

No new unit or integration test is added because this PR mainly removes packaging-time dependency copying and updates dependency coordinates. The behavioral code path is unchanged.

Existing test compilation was updated where the MySQL Connector/J upgrade exposed references to legacy MySQL 5 internal classes.

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

The remaining mysql-connector-java matches are only historical changelog entries. Existing com.mysql.jdbc.Driver string defaults are kept for compatibility and are not bundled driver dependencies.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.94%. Comparing base (a741d4b) to head (85b4df7).

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x    #8119      +/-   ##
============================================
+ Coverage     72.79%   72.94%   +0.15%     
  Complexity      883      883              
============================================
  Files          1327     1327              
  Lines         50719    50719              
  Branches       6049     6049              
============================================
+ Hits          36919    36997      +78     
+ Misses        10803    10721      -82     
- Partials       2997     3001       +4     

see 18 files with indirect coverage changes

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