Drop TimeProvider.Delay

[martintmk]

Details on the issue fix or feature implementation

Closes #1348

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 #1355 (e495375) into main (8f5dc6c) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1355   +/-   ##
=======================================
  Coverage   83.51%   83.51%           
=======================================
  Files         268      268           
  Lines        6362     6362           
  Branches      999      999           
=======================================
  Hits         5313     5313           
  Misses        840      840           
  Partials      209      209           

Flag	Coverage Δ
linux	?
macos	83.51% <ø> (ø)
windows	83.51% <ø> (ø)

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Impacted Files	Coverage Δ
src/Polly.Core/Retry/RetryResilienceStrategy.cs	100.00% <ø> (ø)