Add support for getting/setting the retry attempt number on the context

[BalassaMarton]

Added RetryResilienceContextExtensions with methods for getting/setting the current retry attempt number.
Changed RetryResilienceStrategy to respect and update this property on the context.
Closes #3095

[codecov]

Codecov Report

❌ Patch coverage is 83.33333% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 96.11%. Comparing base (0ce278c) to head (df9d438).
⚠️ Report is 29 commits behind head on main.

Files with missing lines	Patch %	Lines
...lly.Core/Retry/RetryResilienceContextExtensions.cs	80.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3135      +/-   ##
==========================================
- Coverage   96.16%   96.11%   -0.05%     
==========================================
  Files         311      309       -2     
  Lines        7139     7106      -33     
  Branches     1006      999       -7     
==========================================
- Hits         6865     6830      -35     
- Misses        221      222       +1     
- Partials       53       54       +1     

Flag	Coverage Δ
linux	99.91% <83.33%> (+3.75%)	⬆️
macos	96.11% <83.33%> (-0.05%)	⬇️
windows	99.91% <83.33%> (+3.76%)	⬆️

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