Improve AddResilienceStrategy API

[martintmk]

Details on the issue fix or feature implementation

While playing with the DI API I got bothered by the need to access the builder as context.Builder. This PR allows accessing the builder directly so instead of:

services.AddResilienceStrategy("myKey", context => context.Builder.AddTimeout());

We can now do:

// simple case
services.AddResilienceStrategy("myKey", builder => builder.AddTimeout());

// builder + context
services.AddResilienceStrategy("myKey", (builder, context) => builder.AddTimeout());

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 #1183 (c39f67e) into main (cb017af) will increase coverage by 0.00%.
The diff coverage is 100.00%.

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@@           Coverage Diff           @@
##             main    #1183   +/-   ##
=======================================
  Coverage   83.42%   83.42%           
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  Files         273      273           
  Lines        6328     6329    +1     
  Branches     1028     1028           
=======================================
+ Hits         5279     5280    +1     
  Misses        844      844           
  Partials      205      205           

Flag	Coverage Δ
linux	?
macos	83.42% <100.00%> (+<0.01%)	⬆️
windows	83.42% <100.00%> (+<0.01%)	⬆️

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Impacted Files	Coverage Δ
...ependencyInjection/AddResilienceStrategyContext.cs	100.00% <100.00%> (ø)
...tion/ConfigureResilienceStrategyRegistryOptions.cs	100.00% <100.00%> (ø)
...dencyInjection/PollyServiceCollectionExtensions.cs	100.00% <100.00%> (ø)