Drop ResilienceTelemetryFactory

[martintmk]

Details on the issue fix or feature implementation

This PR drops the following public APIs:

• ResilienceTelemetryFactory
• NullResilienceTelemetryFactory
• NullResilienceTelemetry

The ResilienceTelemetry stays public and strategies can use it to report important resilience events. Its signature is expanded to allow passing additional arguments. Internally, ResilienceTelemetry uses DiagnosticSource to report events. In Polly.Extensions we will subscribe to this DiagnosticSource and report the events as logs and metrics.

Additional changes:

• Introduce non-generic Outcome struct.
• Allow to override the default DiagnosticSource by specifying it in ResilienceStrategyBuilder.Properties.

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 #1123 (e5c110e) into main (378500a) will increase coverage by 0.16%.
The diff coverage is 100.00%.

❗ Current head e5c110e differs from pull request most recent head eae2d2f. Consider uploading reports for the commit eae2d2f to get more accurate results

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@@            Coverage Diff             @@
##             main    #1123      +/-   ##
==========================================
+ Coverage   77.71%   77.88%   +0.16%     
==========================================
  Files         200      202       +2     
  Lines        4753     4788      +35     
  Branches      850      858       +8     
==========================================
+ Hits         3694     3729      +35     
  Misses        854      854              
  Partials      205      205              

Flag	Coverage Δ
linux	77.88% <100.00%> (+0.16%)	⬆️
macos	77.88% <100.00%> (+0.16%)	⬆️
windows	77.88% <100.00%> (+0.16%)	⬆️

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

Impacted Files	Coverage Δ
...dencyInjection/PollyServiceCollectionExtensions.cs	100.00% <ø> (ø)
...rc/Polly.Core/Builder/ResilienceStrategyBuilder.cs	100.00% <100.00%> (ø)
...y.Core/Builder/ResilienceStrategyBuilderContext.cs	100.00% <100.00%> (ø)
src/Polly.Core/Retry/RetryResilienceStrategy.cs	100.00% <100.00%> (ø)
src/Polly.Core/Strategy/Outcome.TResult.cs	100.00% <100.00%> (ø)
src/Polly.Core/Strategy/Outcome.cs	100.00% <100.00%> (ø)
src/Polly.Core/Strategy/OutcomePredicate.cs	100.00% <100.00%> (ø)
src/Polly.Core/Telemetry/ResilienceTelemetry.cs	100.00% <100.00%> (ø)
.../Polly.Core/Telemetry/ResilienceTelemetrySource.cs	100.00% <100.00%> (ø)
...rc/Polly.Core/Telemetry/TelemetryEventArguments.cs	100.00% <100.00%> (ø)
... and 4 more

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