Annotate the library with trimming attributes

[martintmk]

Details on the issue fix or feature implementation

Use trimming attributes and resolve the trimming warnings. With this change the AOT compilation works correctly (including the options validation).

Closes #1110

Confirm the following

• I started this PR by branching from the head of the default branch
• I have targeted the PR to merge into the default branch
• I have included unit tests for the issue/feature
• I have successfully run a local build

[codecov]

Codecov Report

Merging #1414 (d111b6b) into main (38d903e) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1414      +/-   ##
==========================================
+ Coverage   83.81%   83.83%   +0.02%     
==========================================
  Files         274      274              
  Lines        6482     6491       +9     
  Branches     1009     1008       -1     
==========================================
+ Hits         5433     5442       +9     
  Misses        840      840              
  Partials      209      209              

Flag	Coverage Δ
linux	83.83% <100.00%> (+0.02%)	⬆️
macos	83.83% <100.00%> (+0.02%)	⬆️
windows	83.83% <100.00%> (+0.02%)	⬆️

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

Impacted Files	Coverage Δ
...r/AdvancedCircuitBreakerStrategyOptions.TResult.cs	100.00% <ø> (ø)
...re/CircuitBreaker/CircuitBreakerStrategyOptions.cs	100.00% <ø> (ø)
.../Polly.Core/ResilienceStrategyBuilderExtensions.cs	100.00% <ø> (ø)
...c/Polly.Core/Retry/RetryStrategyOptions.TResult.cs	100.00% <ø> (ø)
...olly.Core/Telemetry/ResilienceStrategyTelemetry.cs	100.00% <ø> (ø)
...eout/TimeoutResilienceStrategyBuilderExtensions.cs	100.00% <ø> (ø)
src/Polly.Core/Timeout/TimeoutStrategyOptions.cs	100.00% <ø> (ø)
...ions/Registry/ConfigureBuilderContextExtensions.cs	100.00% <ø> (ø)
...s/Telemetry/ResilienceTelemetryDiagnosticSource.cs	100.00% <ø> (ø)
...ry/TelemetryResilienceStrategyBuilderExtensions.cs	100.00% <ø> (ø)
... and 8 more

[martincostello]

Did you mean to delete the line above rather than below?