[repo/AwsInstrumentations] Prepare to .NET9

[Kielek]

Changes

Follow up #2251

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)
• [ ] Unit tests added/updated
• [ ] Appropriate CHANGELOG.md files updated for non-trivial changes
• [ ] Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

Attention: Patch coverage is 90.19608% with 5 lines in your changes missing coverage. Please review.

Project coverage is 83.07%. Comparing base (71655ce) to head (b24b1da).
Report is 569 commits behind head on main.

Files with missing lines	Patch %	Lines
...emetry.Instrumentation.AWS/Implementation/Utils.cs	70.00%	3 Missing ⚠️
...on.AWS/Implementation/AWSTracingPipelineHandler.cs	66.66%	1 Missing ⚠️
...ntation.AWS/Implementation/Tracing/AWSTraceSpan.cs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2272      +/-   ##
==========================================
+ Coverage   73.91%   83.07%   +9.16%     
==========================================
  Files         267       25     -242     
  Lines        9615      585    -9030     
==========================================
- Hits         7107      486    -6621     
+ Misses       2508       99    -2409     

Flag	Coverage Δ
unittests-Instrumentation.AWS	83.07% <90.19%> (?)

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

Files with missing lines	Coverage Δ
...rumentation.AWS/Implementation/AWSServiceHelper.cs	98.64% <100.00%> (-1.36%)	⬇️
...ntation.AWS/Implementation/Metrics/AWSHistogram.cs	87.50% <100.00%> (ø)
...ion.AWS/Implementation/Metrics/AWSMeterProvider.cs	100.00% <100.00%> (ø)
....AWS/Implementation/Metrics/AWSMonotonicCounter.cs	87.50% <100.00%> (ø)
...ion.AWS/Implementation/Metrics/AWSUpDownCounter.cs	93.75% <100.00%> (ø)
...tion.AWS/Implementation/SnsRequestContextHelper.cs	90.90% <100.00%> (-4.10%)	⬇️
...tion.AWS/Implementation/SqsRequestContextHelper.cs	81.81% <100.00%> (-13.19%)	⬇️
...umentation.AWS/Implementation/Tracing/AWSTracer.cs	57.69% <100.00%> (ø)
...on.AWS/Implementation/Tracing/AWSTracerProvider.cs	100.00% <100.00%> (ø)
...on.AWS/Implementation/AWSTracingPipelineHandler.cs	81.57% <66.66%> (-6.18%)	⬇️
... and 2 more

... and 262 files with indirect coverage changes

[Oberon00]

Approving just for the Lambda part

[CodeBlanch]

LGTM

[muhammad-othman]

nit: Do we have to make this change? The previous version was more readable to me.