Specify default action generator for hedging

[martintmk]

Details on the issue fix or feature implementation

I was investigating the original hedging engine and standard hedging pipeline to find a ways to simplify the hedging configuration. A lot of boilerplate in hedging is around specifying the hedging action generator.

However, we can actually allow the default for this generator. In this case the hedging just executes the original callback again ( similar to retries). This can be done by providing the original callback to the generator arguments.

Standard hedging handler can seamlessly integrate into this enhancement by:

• Passing a callback that reads the data from resilience context. (for example cloned request message)
• Taking advantage of the enhanced HedgingActionGeneratorArguments

The simple API addition above will greatly simplify the code in Microsft.Extensions.Http.Resilience library.

On top of that I have also changed the signature of the generator action from Task<TResult> to Task<Outcome<TResult>>. This plays nicely with the overal infrastructure we have. Hedged actions can be optimized to not throw exceptions.

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

[martintmk]

In the follow-up i will do some internal cleanup around hedging. As we can cleanup some internals.

[codecov]

Codecov Report

Merging #1263 (d43f755) into main (e3bf107) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1263      +/-   ##
==========================================
+ Coverage   83.31%   83.33%   +0.01%     
==========================================
  Files         270      270              
  Lines        6312     6317       +5     
  Branches      981      981              
==========================================
+ Hits         5259     5264       +5     
  Misses        844      844              
  Partials      209      209              

Flag	Coverage Δ
linux	?
macos	83.33% <100.00%> (+0.01%)	⬆️
windows	83.33% <100.00%> (+0.01%)	⬆️

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Impacted Files	Coverage Δ
src/Polly.Core/Outcome.cs	100.00% <ø> (ø)
src/Polly.Core/Hedging/Controller/TaskExecution.cs	100.00% <100.00%> (ø)
...Hedging/HedgingActionGeneratorArguments.TResult.cs	100.00% <100.00%> (ø)
src/Polly.Core/Hedging/HedgingHandler.Handler.cs	100.00% <100.00%> (ø)
src/Polly.Core/Hedging/HedgingHandler.TResult.cs	100.00% <100.00%> (ø)
src/Polly.Core/Hedging/HedgingHandler.cs	100.00% <100.00%> (ø)
...lly.Core/Hedging/HedgingStrategyOptions.TResult.cs	100.00% <100.00%> (ø)
src/Polly.Core/Hedging/VoidHedgingHandler.cs	100.00% <100.00%> (ø)