Self-diagnostics - support formatted message for better human readability

[cijothomas]

Fixes #6242

[codecov]

Codecov Report

❌ Patch coverage is 88.46154% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.66%. Comparing base (27234c2) to head (84a1045).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...Telemetry/Internal/SelfDiagnosticsEventListener.cs	75.00%	3 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6411   +/-   ##
=======================================
  Coverage   86.66%   86.66%           
=======================================
  Files         258      258           
  Lines       11858    11873   +15     
=======================================
+ Hits        10277    10290   +13     
- Misses       1581     1583    +2     

Flag	Coverage Δ
unittests-Project-Experimental	86.26% <88.46%> (+<0.01%)	⬆️
unittests-Project-Stable	86.56% <88.46%> (+0.04%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...nTelemetry/Internal/SelfDiagnosticsConfigParser.cs	88.13% <100.00%> (+2.42%)	⬆️
...lemetry/Internal/SelfDiagnosticsConfigRefresher.cs	87.03% <100.00%> (+0.12%)	⬆️
...Telemetry/Internal/SelfDiagnosticsEventListener.cs	96.26% <75.00%> (+0.11%)	⬆️

... and 5 files with indirect coverage changes

[rajkumar-rangaraj]

LGTM

[xiang17]

LGTM with minor feedbacks