optimize undolog manager and fix delete undolog support oracle

[jsbxyyx]

Ⅰ. Describe what this PR did

optimize undo log manager and fix delete undolog support oracle

Ⅱ. Does this pull request fix one issue?

fixes #1596

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

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

[codecov-io]

Codecov Report

Merging #1618 into develop will increase coverage by 0.26%.
The diff coverage is 22.78%.

@@              Coverage Diff              @@
##             develop    #1618      +/-   ##
=============================================
+ Coverage      47.22%   47.48%   +0.26%     
- Complexity      1757     1764       +7     
=============================================
  Files            353      355       +2     
  Lines          12967    12923      -44     
  Branches        1620     1610      -10     
=============================================
+ Hits            6124     6137      +13     
+ Misses          6180     6121      -59     
- Partials         663      665       +2

Impacted Files	Coverage Δ	Complexity Δ
...java/io/seata/rm/datasource/DataSourceManager.java	27.41% <0%> (+1.66%)	7 <0> (ø)	⬇️
...n/java/io/seata/rm/datasource/ConnectionProxy.java	22.88% <0%> (+0.38%)	10 <0> (ø)	⬇️
...asource/src/main/java/io/seata/rm/RMHandlerAT.java	0% <0%> (ø)	0 <0> (ø)	⬇️
.../main/java/io/seata/rm/datasource/AsyncWorker.java	16.43% <0%> (+0.85%)	4 <0> (ø)	⬇️
.../java/io/seata/rm/datasource/DataCompareUtils.java	75.34% <100%> (ø)	25 <0> (ø)	⬇️
...m/datasource/undo/oracle/OracleUndoLogManager.java	3.17% <23.52%> (ø)	2 <2> (?)
.../rm/datasource/undo/mysql/MySQLUndoLogManager.java	3.07% <3.07%> (ø)	2 <2> (?)
...ata/rm/datasource/undo/AbstractUndoLogManager.java	52% <52%> (ø)	10 <10> (?)
...eata/rm/datasource/undo/UndoLogManagerFactory.java	75% <75%> (ø)	2 <2> (?)
... and 2 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update d5b91f3...8be35d5. Read the comment docs.

[slievrly]

LGTM

[zjinlei]

LGTM