Implement HedgingResilienceStrategy

[martintmk]

The issue or feature being addressed

Closes #876

Details on the issue fix or feature implementation

This PR adds all necessary infrastructure and implements Hedging Resilience Strategy.

• When the callbacks are hedged each execution gets its own ResilienceContext and CancellationToken so the concurrent calls won't interfere with each other and can be cancelled individually.
• Once any callback gets acceptable result the properties from cloned ResilienceContext are merged bac to the main one.
• The primary callback still re-uses the main context.

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 #1161 (fac76b3) into main (38ae8fd) will increase coverage by 0.81%.
The diff coverage is 100.00%.

📣 This organization is not using Codecov’s GitHub App Integration. We recommend you install it so Codecov can continue to function properly for your repositories. Learn more

@@            Coverage Diff             @@
##             main    #1161      +/-   ##
==========================================
+ Coverage   82.21%   83.03%   +0.81%     
==========================================
  Files         267      272       +5     
  Lines        5898     6183     +285     
  Branches      967     1006      +39     
==========================================
+ Hits         4849     5134     +285     
  Misses        844      844              
  Partials      205      205              

Flag	Coverage Δ
linux	?
macos	?
windows	83.03% <100.00%> (+0.81%)	⬆️

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

Impacted Files	Coverage Δ
src/Polly.Core/Hedging/HedgingConstants.cs	100.00% <ø> (ø)
...c/Polly.Core/Hedging/Controller/ContextSnapshot.cs	100.00% <100.00%> (ø)
...Polly.Core/Hedging/Controller/HedgingController.cs	100.00% <100.00%> (ø)
...Core/Hedging/Controller/HedgingExecutionContext.cs	100.00% <100.00%> (ø)
src/Polly.Core/Hedging/Controller/TaskExecution.cs	100.00% <100.00%> (ø)
...Hedging/HedgingActionGeneratorArguments.TResult.cs	100.00% <100.00%> (ø)
...ly.Core/Hedging/HedgingActionGeneratorArguments.cs	100.00% <100.00%> (ø)
src/Polly.Core/Hedging/HedgingHandler.Handler.cs	100.00% <100.00%> (ø)
src/Polly.Core/Hedging/HedgingHandler.cs	100.00% <100.00%> (ø)
...rc/Polly.Core/Hedging/HedgingResilienceStrategy.cs	100.00% <100.00%> (ø)
... and 6 more