optimize: optimize RegistryFactory singleton pattern and RegistryType judge mode

[ph3636]

… judge mode

Ⅰ. Describe what this PR did

optimize RegistryFactory singleton pattern and RegistryType judge mode

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-io]

Codecov Report

Merging #2382 into develop will increase coverage by 0.03%.
The diff coverage is 0%.

@@              Coverage Diff              @@
##             develop    #2382      +/-   ##
=============================================
+ Coverage      51.83%   51.86%   +0.03%     
+ Complexity      2702     2701       -1     
=============================================
  Files            517      517              
  Lines          16776    16768       -8     
  Branches        2033     2027       -6     
=============================================
+ Hits            8695     8697       +2     
+ Misses          7272     7260      -12     
- Partials         809      811       +2

Impacted Files	Coverage Δ	Complexity Δ
...a/io/seata/discovery/registry/RegistryFactory.java	0% <0%> (ø)	0 <0> (ø)	⬇️
...java/io/seata/discovery/registry/RegistryType.java	0% <0%> (ø)	0 <0> (ø)	⬇️
...o/seata/server/coordinator/DefaultCoordinator.java	54.35% <0%> (-0.52%)	28% <0%> (-1%)
...in/java/io/seata/server/session/GlobalSession.java	84% <0%> (-0.45%)	72% <0%> (-1%)
...server/store/file/FileTransactionStoreManager.java	57.14% <0%> (+0.63%)	30% <0%> (+1%)	⬆️
...a/io/seata/core/rpc/netty/AbstractRpcRemoting.java	11.55% <0%> (+1%)	4% <0%> (ø)	⬇️

[xingfudeshi]

LGTM.

[zjinlei]

LGTM