optimize: the thread pool size of branchResultMessageExecutor

[tuwenlin]

branchResultMessageExecutor只用来处理分支事务响应

coreSize和maxSize都改为2倍核心线程数

[codecov-commenter]

Codecov Report

Merging #4670 (7236e0a) into develop (a43beb4) will decrease coverage by 0.03%.
The diff coverage is 0.00%.

@@              Coverage Diff              @@
##             develop    #4670      +/-   ##
=============================================
- Coverage      48.64%   48.61%   -0.04%     
+ Complexity      4044     4042       -2     
=============================================
  Files            734      734              
  Lines          25581    25583       +2     
  Branches        3157     3157              
=============================================
- Hits           12444    12437       -7     
- Misses         11802    11808       +6     
- Partials        1335     1338       +3     

Impacted Files	Coverage Δ
...ava/io/seata/core/rpc/netty/NettyServerConfig.java	0.00% <0.00%> (ø)
...n/src/main/java/io/seata/common/util/IdWorker.java	77.08% <0.00%> (-6.25%)	⬇️
...very/registry/zk/ZookeeperRegisterServiceImpl.java	61.02% <0.00%> (-0.74%)	⬇️
...torage/file/store/FileTransactionStoreManager.java	56.12% <0.00%> (-0.65%)	⬇️
...erver/storage/file/session/FileSessionManager.java	49.04% <0.00%> (-0.64%)	⬇️

[funky-eyes]

LGTM

[slievrly]

LGTM