[To dev/1.3] Clean up dead RPC thread config and use node-specific selectorNum

[JackieTien97]

cp from #17551

[sonarqubecloud]

Quality Gate passed

Issues
3 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

❌ Patch coverage is 53.23741% with 65 lines in your changes missing coverage. Please review.
✅ Project coverage is 41.75%. Comparing base (8dc2e37) to head (5354d7e).
⚠️ Report is 1 commits behind head on dev/1.3.

Files with missing lines	Patch %	Lines
...apache/iotdb/commons/client/ClientPoolFactory.java	17.24%	24 Missing ⚠️
...he/iotdb/confignode/conf/ConfigNodeDescriptor.java	0.00%	12 Missing ⚠️
...ion/config/executor/ClusterConfigTaskExecutor.java	0.00%	8 Missing ⚠️
...apache/iotdb/confignode/conf/ConfigNodeConfig.java	54.54%	5 Missing ⚠️
...sync/CnToCnInternalServiceAsyncRequestManager.java	0.00%	3 Missing ⚠️
...t/cn/DnToCnInternalServiceAsyncRequestManager.java	0.00%	2 Missing ⚠️
...dn/DataNodeExternalServiceAsyncRequestManager.java	0.00%	2 Missing ⚠️
...ient/dn/DataNodeMPPServiceAsyncRequestManager.java	0.00%	2 Missing ⚠️
...t/dn/DnToDnInternalServiceAsyncRequestManager.java	0.00%	2 Missing ⚠️
.../ConfigNodeInternalServiceAsyncRequestManager.java	0.00%	2 Missing ⚠️
... and 3 more

Additional details and impacted files

@@              Coverage Diff              @@
##             dev/1.3   #17618      +/-   ##
=============================================
- Coverage      41.76%   41.75%   -0.02%     
  Complexity       241      241              
=============================================
  Files           3611     3611              
  Lines         238153   238173      +20     
  Branches       28920    28928       +8     
=============================================
- Hits           99468    99445      -23     
- Misses        138685   138728      +43     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.