feature: support polardb-x 2.0

[hsien999]

• I have registered the PR changes.

Ⅰ. Describe what this PR did

Extending AT mode support for PolarDB-X 2.0.
Note: Transparent PolarDB-X support is currently available only in the form of MySQL inheritance, and DRDS partitioning may need to be supported in the future.

Ⅱ. Does this pull request fix one issue?

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

Merging #5907 (6905b02) into 2.x (5c28eeb) will increase coverage by 0.01%.
The diff coverage is 56.97%.

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x    #5907      +/-   ##
============================================
+ Coverage     48.76%   48.78%   +0.01%     
- Complexity     4434     4465      +31     
============================================
  Files           819      837      +18     
  Lines         28610    28689      +79     
  Branches       3569     3572       +3     
============================================
+ Hits          13951    13995      +44     
- Misses        13197    13231      +34     
- Partials       1462     1463       +1     

Files	Coverage Δ
...n/src/main/java/io/seata/common/util/PageUtil.java	50.00% <ø> (ø)
...tasource/exec/polardbx/PolarDBXInsertExecutor.java	100.00% <100.00%> (ø)
...ardbx/PolarDBXInsertOnDuplicateUpdateExecutor.java	100.00% <100.00%> (ø)
...ce/sql/handler/polardbx/PolarDBXEscapeHandler.java	100.00% <100.00%> (ø)
...urce/undo/polardbx/PolarDBXUndoDeleteExecutor.java	100.00% <100.00%> (ø)
...tasource/undo/polardbx/PolarDBXUndoLogManager.java	100.00% <100.00%> (ø)
...urce/undo/polardbx/PolarDBXUndoUpdateExecutor.java	100.00% <100.00%> (ø)
...sqlparser/druid/DruidSQLRecognizerFactoryImpl.java	69.23% <100.00%> (ø)
...arser/druid/polardbx/PolarDBXDeleteRecognizer.java	100.00% <100.00%> (ø)
...arser/druid/polardbx/PolarDBXInsertRecognizer.java	100.00% <100.00%> (ø)
... and 13 more

... and 6 files with indirect coverage changes

[slievrly]

add change in 2.0.0.md

[slievrly]

LGTM