Fix hedging being cancelled too early

[martintmk]

Details on the issue fix or feature implementation

Hedging strategy should respect the original cancellation token otherwise inner strategy that replaces the cancellation token (TimeoutStrategy) can temporarily replace it and hedging will start accepting it. This could cause early hedging cancellation.

Added a test that demonstrates the issue.

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 #1340 (7f98d79) into main (18171df) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #1340   +/-   ##
=======================================
  Coverage   83.54%   83.54%           
=======================================
  Files         270      270           
  Lines        6374     6374           
  Branches     1003     1003           
=======================================
  Hits         5325     5325           
  Misses        840      840           
  Partials      209      209           

Flag	Coverage Δ
linux	83.54% <100.00%> (ø)
macos	83.54% <100.00%> (ø)
windows	83.54% <100.00%> (ø)

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Impacted Files	Coverage Δ
...rc/Polly.Core/Hedging/HedgingResilienceStrategy.cs	100.00% <100.00%> (ø)