Introduce ResilienceStrategyBuilder.Validator

[martintmk]

Details on the issue fix or feature implementation

This API addition allows the library to inject their own validator and get rid of the reflection that is used in the default validator.
This allows the library that consumes the Polly to be AOT compatible.

In ideal world we could just use the generators introduced by dotnet/runtime#85475.
However, this would pull the heavy Microsoft.Extensions.Options dependency into the core package.

As a follow-up task after #1360 is merged we can introduce ResilienceValidator.Validate utility API in Polly.Extensions that uses generated validators for validation and doesn't use reflection at all (for all built-in options).

Contributes to #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 #1412 (5376066) into main (1acb88a) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1412      +/-   ##
==========================================
+ Coverage   83.78%   83.81%   +0.03%     
==========================================
  Files         273      274       +1     
  Lines        6470     6482      +12     
  Branches     1008     1009       +1     
==========================================
+ Hits         5421     5433      +12     
  Misses        840      840              
  Partials      209      209              

Flag	Coverage Δ
linux	83.81% <100.00%> (+0.03%)	⬆️
macos	?
windows	?

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Impacted Files	Coverage Δ
.../Polly.Core/Registry/ResilienceStrategyRegistry.cs	100.00% <100.00%> (ø)
src/Polly.Core/ResilienceStrategyBuilderBase.cs	100.00% <100.00%> (ø)
src/Polly.Core/ResilienceValidationContext.cs	100.00% <100.00%> (ø)
...ry/TelemetryResilienceStrategyBuilderExtensions.cs	100.00% <100.00%> (ø)