The deafult RateLimiterStrategyOptions instance is now valid

[martintmk]

Details on the issue fix or feature implementation

The #1313 got me thinking that RateLimiterStrategyOptions will be the only options that is invalid by default.

We can address that by introducing RateLimiterStrategyOptions.DefaultRateLimiterOptions property that will be used unless someone explicitly assigns RateLimiterStrategyOptions.RateLimiter.

This provides a nice out-of-box experience.

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]

Nice change.

[codecov]

Codecov Report

Merging #1315 (999ce70) into main (4524822) will increase coverage by 0.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1315      +/-   ##
==========================================
+ Coverage   83.28%   83.33%   +0.04%     
==========================================
  Files         264      264              
  Lines        6301     6318      +17     
  Branches      997      998       +1     
==========================================
+ Hits         5248     5265      +17     
  Misses        844      844              
  Partials      209      209              

Flag	Coverage Δ
linux	?
macos	83.33% <100.00%> (+0.04%)	⬆️
windows	83.33% <100.00%> (?)

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

Impacted Files	Coverage Δ
.../RateLimiterResilienceStrategyBuilderExtensions.cs	100.00% <100.00%> (ø)
...c/Polly.RateLimiting/RateLimiterStrategyOptions.cs	100.00% <100.00%> (ø)

... and 4 files with indirect coverage changes