Finalize the callback API

[martintmk]

Details on the issue fix or feature implementation

This PR finalizes and cleans-up the callback API.

• Introducing NoOutcomeGenerator and dropping TimeoutGenerator
• Introducing TResult based class for Generators and Events
• To verify the API a new generic ResilienceStrategyOptions<TResult> are introduced. The user will use these when they care only about specific result type. These can be easily converted to ResilienceStrategyOptions.

I hope with this PR the callback API is almost done only minor changes (if any) will be done later.

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-commenter]

Codecov Report

Merging #1137 (de36128) into main (2aea2f2) will increase coverage by 0.33%.
The diff coverage is 100.00%.

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@@            Coverage Diff             @@
##             main    #1137      +/-   ##
==========================================
+ Coverage   78.14%   78.48%   +0.33%     
==========================================
  Files         201      204       +3     
  Lines        4846     4922      +76     
  Branches      863      869       +6     
==========================================
+ Hits         3787     3863      +76     
  Misses        854      854              
  Partials      205      205              

Flag	Coverage Δ
linux	78.48% <100.00%> (+0.33%)	⬆️
macos	?
windows	78.48% <100.00%> (+0.33%)	⬆️

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

Impacted Files	Coverage Δ
.../Retry/RetryResilienceStrategyBuilderExtensions.cs	100.00% <100.00%> (ø)
...c/Polly.Core/Retry/RetryStrategyOptions.TResult.cs	100.00% <100.00%> (ø)
src/Polly.Core/Strategy/NoOutcomeGenerator.cs	100.00% <100.00%> (ø)
src/Polly.Core/Strategy/OutcomeEvent.Handler.cs	100.00% <100.00%> (ø)
src/Polly.Core/Strategy/OutcomeEvent.TResult.cs	100.00% <100.00%> (ø)
src/Polly.Core/Strategy/OutcomeEvent.cs	100.00% <100.00%> (ø)
...rc/Polly.Core/Strategy/OutcomeGenerator.Handler.cs	100.00% <100.00%> (ø)
...rc/Polly.Core/Strategy/OutcomeGenerator.TResult.cs	100.00% <100.00%> (ø)
src/Polly.Core/Strategy/OutcomeGenerator.cs	100.00% <100.00%> (ø)
src/Polly.Core/Strategy/OutcomePredicate.cs	100.00% <100.00%> (ø)
... and 2 more

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