Introduce TelemetryResilienceStrategyOptions.ResultFormatter

[martintmk]

Details on the issue fix or feature implementation

One very common scenario when using ResilienceStrategy is to handle HttpResponseMessage.

The built-in telemetry now logs the whole result simply by formatting it to string. For HttpResponseMessage this can be noisy, non-performant and could reveal sensitive data as demonstrated bellow:

var response = new HttpResponseMessage(System.Net.HttpStatusCode.OK);
response.Headers.Add("Header1", "value");
response.Headers.Add("Header2", "Sensitive Value");
response.Content = new StringContent("Sensitive Content");

StatusCode: 200, ReasonPhrase: 'OK', Version: 1.1, Content: System.Net.Http.StringContent, Headers:
{
  Header1: value
  Header2: Sensitive Value
  Content-Type: text/plain; charset=utf-8
}

This PR allows customization of how the results are formatted and also changes the default formatting behavior for HttpResponseMessage.

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]

Suggested change

	/// Defaults to a formatter that returns a status code for HTTP based responses and result as-is for all other result types.
	/// Defaults to a formatter that returns a status code for HTTP based responses and the result as-is for all other result types.

[codecov]

Codecov Report

Merging #1294 (53a9ad6) into main (cd9c59e) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1294      +/-   ##
==========================================
+ Coverage   83.26%   83.28%   +0.02%     
==========================================
  Files         263      263              
  Lines        6291     6299       +8     
  Branches      993      994       +1     
==========================================
+ Hits         5238     5246       +8     
  Misses        844      844              
  Partials      209      209              

Flag	Coverage Δ
linux	83.28% <100.00%> (+0.02%)	⬆️
macos	83.28% <100.00%> (+0.02%)	⬆️
windows	?

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

Impacted Files	Coverage Δ
...xtensions/Telemetry/TelemetryResilienceStrategy.cs	100.00% <100.00%> (ø)
...ry/TelemetryResilienceStrategyBuilderExtensions.cs	100.00% <100.00%> (ø)
...ns/Telemetry/TelemetryResilienceStrategyOptions.cs	100.00% <100.00%> (ø)