Hide/drop some unused APIs

[martintmk]

Details on the issue fix or feature implementation

Just going through the APIs and trimming some fat. All these are easy to add back of there is a need for it.

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]

Codecov Report

Merging #1491 (487a611) into main (9fd37be) will decrease coverage by 0.09%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1491      +/-   ##
==========================================
- Coverage   83.71%   83.63%   -0.09%     
==========================================
  Files         272      272              
  Lines        6424     6390      -34     
  Branches     1012     1010       -2     
==========================================
- Hits         5378     5344      -34     
  Misses        837      837              
  Partials      209      209              

Flag	Coverage Δ
linux	83.63% <100.00%> (-0.09%)	⬇️
macos	83.63% <100.00%> (-0.09%)	⬇️
windows	83.63% <100.00%> (-0.09%)	⬇️

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

Files Changed	Coverage Δ
...Core/Registry/ResiliencePipelineRegistryOptions.cs	100.00% <ø> (ø)
src/Polly.Core/ResiliencePropertyKey.cs	100.00% <ø> (ø)
src/Polly.Core/Telemetry/TelemetryUtil.cs	100.00% <ø> (ø)
...xtensions/Telemetry/ResilienceContextExtensions.cs	100.00% <ø> (ø)
src/Polly.Core/Registry/ConfigureBuilderContext.cs	100.00% <100.00%> (ø)
.../Polly.Core/Registry/ResiliencePipelineRegistry.cs	100.00% <100.00%> (ø)
src/Polly.Core/ResilienceContext.cs	100.00% <100.00%> (ø)
src/Polly.Core/ResiliencePipelineBuilderBase.cs	100.00% <100.00%> (ø)
src/Polly.Core/StrategyBuilderContext.cs	100.00% <100.00%> (ø)
...ependencyInjection/AddResiliencePipelineContext.cs	100.00% <100.00%> (ø)
... and 1 more