[Proposal] Introduce ResilienceStrategyBuilderBase

[martintmk]

Details on the issue fix or feature implementation

One thing I wasn't a big fan of was the duplications of extensions for non-reactive strategies such as Timeout or RateLimiter.

In this PR I am introducing ResilienceStrategyBuilderBase class. The extensibility author can use is to target extensions that work for both generic and non-generic strategies.

This way full set of extensions are always exposed for both generic and non-generic builders and there are no duplications.

The extension bellow will be visible for both builder types:

public static TBuilder AddTimeout<TBuilder>(this TBuilder builder, TimeoutStrategyOptions options)
    where TBuilder : ResilienceStrategyBuilderBase
{
    builder.AddStrategy(context => new TimeoutResilienceStrategy(options, context.TimeProvider, context.Telemetry), options);
    return builder;
}

I have dropped a bunch of duplicate extensions.

What do you think about this idea?

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

[martincostello]

This seems reasonable to me.

[codecov]

Codecov Report

Merging #1236 (e69d105) into main (141bd0a) will decrease coverage by 0.11%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1236      +/-   ##
==========================================
- Coverage   82.91%   82.81%   -0.11%     
==========================================
  Files         262      263       +1     
  Lines        6141     6103      -38     
  Branches      966      966              
==========================================
- Hits         5092     5054      -38     
  Misses        844      844              
  Partials      205      205              

Flag	Coverage Δ
linux	82.81% <100.00%> (-0.11%)	⬇️
macos	82.81% <100.00%> (-0.11%)	⬇️
windows	?

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Impacted Files	Coverage Δ
...ry/TelemetryResilienceStrategyBuilderExtensions.cs	100.00% <ø> (ø)
...rcuitBreakerResilienceStrategyBuilderExtensions.cs	100.00% <100.00%> (ø)
...rc/Polly.Core/ResilienceStrategyBuilder.TResult.cs	100.00% <100.00%> (ø)
src/Polly.Core/ResilienceStrategyBuilder.cs	100.00% <100.00%> (ø)
.../Retry/RetryResilienceStrategyBuilderExtensions.cs	100.00% <100.00%> (ø)
...lly.Core/Strategy/ResilienceStrategyBuilderBase.cs	100.00% <100.00%> (ø)
...eout/TimeoutResilienceStrategyBuilderExtensions.cs	100.00% <100.00%> (ø)
.../RateLimiterResilienceStrategyBuilderExtensions.cs	100.00% <100.00%> (ø)