Introduce RetryResilienceStrategy

[martintmk]

The issue or feature being addressed

Contributes to #1093

Details on the issue fix or feature implementation

This PR adds the retry resilience strategy to V8. Only core functionality added for now, to be expanded later.

Some missing pieces:

• In the follow-up we should add RetryBackoffType.ExponentialWithJitter
• More convenience extensions to RetryResilienceStrategyBuilderExtensions (custom retries, OnRetry callbacks)

Usage:

var builder = new ResilienceStrategyBuilder();

// using the options
builder.AddRetry(new RetryStrategyOptions
{
    ShouldRetry = new ShouldRetryPredicate()
        .Exception<HttpRequestException>()
        .Result<HttpResponseMessage>(response => !response.IsSuccessStatusCode)
});

// no retry delay
builder.AddRetry(new RetryStrategyOptions
{
    ShouldRetry = new ShouldRetryPredicate()
        .Exception<HttpRequestException>()
        .Result<HttpResponseMessage>(response => !response.IsSuccessStatusCode),
   RetryDelay = TimeSpan.Zero
});


// convenience overloads
builder.AddRetry(retry => retry
    .Exception<HttpRequestException>()
    .Result<HttpResponseMessage>(response => !response.IsSuccessStatusCode)); 

// using the options (complex)
builder.AddRetry(new RetryStrategyOptions
{
    ShouldRetry = new ShouldRetryPredicate()
        .Exception<HttpRequestException>()
        .Result<HttpResponseMessage>(response => !response.IsSuccessStatusCode),
    BackoffType = RetryBackoffType.Linear,
    RetryCount = 2,
    BaseDelay = TimeSpan.FromSeconds(1),
    OnRetry = new OnRetryEvent().Add<HttpResponseMessage>(() => Console.WriteLine("On retry")),
    RetryDelayGenerator = new RetryDelayGenerator().SetGenerator<HttpResponseMessage>((outcome, args) =>
    {
        if (outcome.HasResult && outcome.Result.Headers.TryGetValues("Retry-After", out var values))
        {
            return TimeSpan.FromSeconds(int.Parse(values.First()));
        }

        return args.DelayHint;
    })
});

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 #1101 (1d008c2) into main (40606d2) will increase coverage by 0.60%.
The diff coverage is 100.00%.

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@@            Coverage Diff             @@
##             main    #1101      +/-   ##
==========================================
+ Coverage   76.35%   76.96%   +0.60%     
==========================================
  Files         185      191       +6     
  Lines        4479     4597     +118     
  Branches      821      838      +17     
==========================================
+ Hits         3420     3538     +118     
  Misses        854      854              
  Partials      205      205              

Flag	Coverage Δ
linux	76.96% <100.00%> (+0.60%)	⬆️
macos	?
windows	?

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

Impacted Files	Coverage Δ
src/Polly.Core/Strategy/SimpleEvent.cs	100.00% <ø> (ø)
...rc/Polly.Core/Telemetry/NullResilienceTelemetry.cs	100.00% <ø> (ø)
src/Polly.Core/Retry/OnRetryArguments.cs	100.00% <100.00%> (ø)
src/Polly.Core/Retry/RetryConstants.cs	100.00% <100.00%> (ø)
src/Polly.Core/Retry/RetryDelayArguments.cs	100.00% <100.00%> (ø)
src/Polly.Core/Retry/RetryDelayGenerator.cs	100.00% <100.00%> (ø)
src/Polly.Core/Retry/RetryHelper.cs	100.00% <100.00%> (ø)
src/Polly.Core/Retry/RetryResilienceStrategy.cs	100.00% <100.00%> (ø)
.../Retry/RetryResilienceStrategyBuilderExtensions.cs	100.00% <100.00%> (ø)
src/Polly.Core/Retry/RetryStrategyOptions.cs	100.00% <100.00%> (ø)
... and 2 more

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[geeknoid]

In general, I recommend switching to use helpers for throwing exceptions in the code base. Helpers reduce code size and improve i-cache efficiency.

[martintmk]

I tried it here, but it doesn't work because switch expression expects the TimeSpan result type.

error CS0029: Cannot implicitly convert type 'void' to 'System.TimeSpan'

I'll leave it as it is for now.