Threads renaming follow up

[vlntb]

High Level Overview of Change

This update builds on the thread-renaming PR (#6212).
It clarifies thread names to reduce ambiguity in performance monitoring tools.
No functional changes.

Context of Change

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactor (non-breaking change that only restructures code)
• Performance (increase or change in throughput and/or latency)
• Tests (you added tests for code that already exists, or your new feature included in this PR)
• Documentation update
• Chore (no impact to binary, e.g. .gitignore, formatting, dropping support for older tooling)
• Release

API Impact

• Public API: New feature (new methods and/or new fields)
• Public API: Breaking change (in general, breaking changes should only impact the next api_version)
• libxrpl change (any change that may affect libxrpl or dependents of libxrpl)
• Peer protocol change (must be backward compatible or bump the peer protocol version)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.9%. Comparing base (bf4674f) to head (c6ad348).
⚠️ Report is 1 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #6336     +/-   ##
=========================================
- Coverage     79.9%   79.9%   -0.0%     
=========================================
  Files          840     840             
  Lines        65483   65483             
  Branches      7249    7253      +4     
=========================================
- Hits         52318   52313      -5     
- Misses       13165   13170      +5     

Files with missing lines	Coverage Δ
src/xrpld/app/main/Main.cpp	77.9% <100.0%> (ø)

... and 4 files with indirect coverage changes

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[lmaisons]

As requested.