bugfix: Resolve MySQL Driver Loading Issue (#6760)

[lyl2008dsg]

• I have registered the PR changes.

Ⅰ. Describe what this PR did

This PR resolves the issue of the MySQL driver not loading when starting the apache/seata-server:2.1.0.jre17 Docker image. The fix involves removing the custom classloader setup and relying on the default classloader to handle the MySQL driver loading. Additionally, the MySQL driver jar has been moved from the lib/jdbc directory to the lib directory, simplifying the path and ensuring the driver is loaded properly.

Ⅱ. Does this pull request fix one issue?

fixes #6760

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

The changes made pertain to configuration and environment setup, which are typically validated through deployment tests rather than unit or integration tests. Future contributions could focus on creating automated tests for Docker image configurations to ensure environment consistency.

Ⅳ. Describe how to verify it

To verify this fix:

1. Ensure the MySQL driver jar is now located in the lib directory.
2. Start the Seata server using the updated configuration.
3. Check that the MySQL driver is loaded correctly without any errors during the initialization process.
4. Optionally, connect to a MySQL database to confirm that database connectivity is functioning correctly.
5. Additionally, Perform a build using the specific Maven profile:
   • Run mvn clean install -P release-seata to build the project.
   • Navigate to incubator-seata/distribution/target/apache-seata-x.x.x-incubating-bin/apache-seata/bin and execute seata-server.sh.
   • Ensure the application starts up correctly, referring to the application.yml settings for seata.config.type: file, and check the logs to verify that the store.db.driverClassName = com.mysql.cj.jdbc.Driver setting from file.conf is correctly utilized.

Ⅴ. Special notes for reviews

Please focus on the changes made to the classloader behavior and the repositioning of the MySQL driver jar. Confirm that these changes align with best practices for Docker and Java application deployments. Additionally, verify that the removal of custom classloader settings does not inadvertently affect other aspects of the system's behavior.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 52.22%. Comparing base (64035c5) to head (eb586be).
Report is 2 commits behind head on 2.x.

Files	Patch %	Lines
...eata/core/store/db/AbstractDataSourceProvider.java	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x    #6765      +/-   ##
============================================
+ Coverage     52.15%   52.22%   +0.06%     
  Complexity     6294     6294              
============================================
  Files          1064     1064              
  Lines         37215    37179      -36     
  Branches       4417     4417              
============================================
+ Hits          19411    19415       +4     
+ Misses        15883    15848      -35     
+ Partials       1921     1916       -5     

Files	Coverage Δ
...eata/core/store/db/AbstractDataSourceProvider.java	0.00% <0.00%> (ø)

... and 4 files with indirect coverage changes

[funky-eyes]

LGTM