Simplify file names

[martintmk]

Details on the issue fix or feature implementation

Simplify the file-names around ResilienceStrategy.

Additionally, I have renamed the OutcomeResilienceStrategy to ReactiveResilienceStrategy to better align with used terminology.

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 #1455 (c74dc4c) into main (0f38c51) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #1455   +/-   ##
=======================================
  Coverage   83.92%   83.92%           
=======================================
  Files         273      274    +1     
  Lines        6506     6506           
  Branches     1012     1012           
=======================================
  Hits         5460     5460           
  Misses        837      837           
  Partials      209      209           

Flag	Coverage Δ
linux	83.92% <100.00%> (ø)
macos	83.92% <100.00%> (ø)
windows	83.92% <100.00%> (ø)

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

Files Changed	Coverage Δ
...CircuitBreaker/CircuitBreakerResilienceStrategy.cs	100.00% <ø> (ø)
.../Polly.Core/Fallback/FallbackResilienceStrategy.cs	100.00% <ø> (ø)
...rc/Polly.Core/Hedging/HedgingResilienceStrategy.cs	100.00% <ø> (ø)
src/Polly.Core/ReactiveResilienceStrategy.cs	100.00% <ø> (ø)
src/Polly.Core/ResilienceStrategy.Async.cs	100.00% <ø> (ø)
src/Polly.Core/ResilienceStrategy.AsyncT.cs	100.00% <ø> (ø)
src/Polly.Core/ResilienceStrategyT.Async.cs	100.00% <ø> (ø)
src/Polly.Core/ResilienceStrategyT.Sync.cs	100.00% <ø> (ø)
src/Polly.Core/Retry/RetryResilienceStrategy.cs	100.00% <ø> (ø)
src/Polly.Core/ResilienceStrategyT.cs	100.00% <100.00%> (ø)