optimize: modify the semantics of RaftServerFactory and remove unnecessary singleton

[funky-eyes]

• I have registered the PR changes.

Ⅰ. Describe what this PR did

Ⅱ. Does this pull request fix one issue?

fixes #6083

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 #6089 (c8136dd) into 2.x (9fef2db) will decrease coverage by 0.05%.
The diff coverage is 66.07%.

❗ Current head c8136dd differs from pull request most recent head 186a7f6. Consider uploading reports for the commit 186a7f6 to get more accurate results

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x    #6089      +/-   ##
============================================
- Coverage     49.53%   49.49%   -0.05%     
+ Complexity     4783     4758      -25     
============================================
  Files           909      909              
  Lines         31418    31388      -30     
  Branches       3778     3782       +4     
============================================
- Hits          15563    15534      -29     
+ Misses        14316    14313       -3     
- Partials       1539     1541       +2     

Files	Coverage Δ
...o/seata/server/cluster/raft/util/RaftTaskUtil.java	28.00% <100.00%> (ø)
...in/java/io/seata/server/session/SessionHolder.java	52.81% <100.00%> (ø)
...io/seata/server/cluster/raft/RaftStateMachine.java	61.11% <0.00%> (-1.39%)	⬇️
...erver/storage/raft/lock/RaftDistributedLocker.java	20.00% <0.00%> (ø)
.../snapshot/metadata/LeaderMetadataSnapshotFile.java	16.66% <0.00%> (-0.58%)	⬇️
...in/java/io/seata/server/session/GlobalSession.java	72.96% <0.00%> (ø)
.../io/seata/server/controller/ClusterController.java	8.69% <0.00%> (ø)
...o/seata/server/cluster/raft/RaftServerManager.java	85.71% <78.04%> (ø)

... and 7 files with indirect coverage changes

[leizhiyuan]

LGTM