Introduce unit-tests for issues fixed in v8

[martintmk]

Details on the issue fix or feature implementation

Here we add unit tests for issues addressed in v8. This demonstrates the issue reporters the problem is fixed in v8.

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 #1157 (959fe43) into main (2d47e4f) will increase coverage by 0.45%.
The diff coverage is 100.00%.

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@@            Coverage Diff             @@
##             main    #1157      +/-   ##
==========================================
+ Coverage   83.03%   83.49%   +0.45%     
==========================================
  Files         272      272              
  Lines        6183     6355     +172     
  Branches     1006     1018      +12     
==========================================
+ Hits         5134     5306     +172     
  Misses        844      844              
  Partials      205      205              

Flag	Coverage Δ
macos	?
windows	83.49% <100.00%> (+0.45%)	⬆️

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

Impacted Files	Coverage Δ
...Core/Hedging/Controller/HedgingExecutionContext.cs	100.00% <100.00%> (ø)
src/Polly.Core/Hedging/Controller/TaskExecution.cs	100.00% <100.00%> (ø)

... and 6 files with indirect coverage changes

[martintmk]

I think we can just merge this PR and keep the branch. It just adds more tests which is useful to have in main.