optimize: datasource auto proxy

[selfishlover]

Ⅰ. Describe what this PR did

Simplify the logic of datasource auto proxy, reduce redundant code by merging them into one processor.

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

Added an integration test which simulates 3 major ways how user would register their DataSource bean.

Ⅳ. Describe how to verify it

Add project's spring boot starter to your project dependency, register Datasource bean in the way you like, test GlobalLock or GlobalTransaction to see whether it works. Or just run the new integration test to verify it.
fixes #3701

[codecov-commenter]

Codecov Report

Merging #3588 (06f7413) into develop (23f4933) will increase coverage by 0.24%.
The diff coverage is 70.37%.

@@              Coverage Diff              @@
##             develop    #3588      +/-   ##
=============================================
+ Coverage      51.63%   51.88%   +0.24%     
- Complexity      3518     3533      +15     
=============================================
  Files            640      639       -1     
  Lines          21420    21408      -12     
  Branches        2671     2665       -6     
=============================================
+ Hits           11061    11108      +47     
+ Misses          9253     9191      -62     
- Partials        1106     1109       +3     

Impacted Files	Coverage Δ	Complexity Δ
...utoconfigure/SeataDataSourceAutoConfiguration.java	0.00% <ø> (ø)	0.00 <0.00> (ø)
...ation/datasource/AutoDataSourceProxyRegistrar.java	0.00% <ø> (ø)	0.00 <0.00> (ø)
...ion/datasource/SeataAutoDataSourceProxyAdvice.java	70.83% <66.66%> (+70.83%)	3.00 <3.00> (+3.00)
...on/datasource/SeataAutoDataSourceProxyCreator.java	69.44% <69.69%> (+69.44%)	8.00 <6.00> (+8.00)
...g/annotation/datasource/DataSourceProxyHolder.java	75.00% <100.00%> (+75.00%)	3.00 <3.00> (+3.00)
...torage/file/store/FileTransactionStoreManager.java	57.69% <0.00%> (+0.64%)	29.00% <0.00%> (+1.00%)

[xingfudeshi]

LGTM.

[funky-eyes]

LGTM