GPL fix (#2457)

[ti-chi-bot]

This is an automated cherry-pick of #2457

What problem does this PR solve?

If mysql-connector-J with the GPL license is included, then the license of TiSpark will also be polluted as GPL

What is changed and how it works?

upgrade mysql-connector-java from 5.1.49 to 8.0.29 and remove it from the TiSpark'jar to avoid GPL pollution.

Btw, change little tests to be compatible with the upgraded mysql-connector-java.

doc: https://github.com/pingcap/tispark/wiki/Getting-TiSpark#getting-mysql-connector-j

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

Code changes

• pom changed
• some test changed

Side effects

• Breaking backward compatibility

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation
• Need to be included in the release note

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• shiyuhang0
• xuanyu66

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[shiyuhang0]

/run-all-tests

[shiyuhang0]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 04fb397