Hide CircuitBreakerStateProvider.LastHandledOutcome

[martintmk]

Details on the issue fix or feature implementation

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Contributes to #1301

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 #1446 (08dfec5) into main (2f10d19) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1446   +/-   ##
=======================================
  Coverage   83.90%   83.90%           
=======================================
  Files         273      273           
  Lines        6516     6516           
  Branches     1012     1012           
=======================================
  Hits         5467     5467           
  Misses        840      840           
  Partials      209      209           

Flag	Coverage Δ
macos	83.90% <0.00%> (ø)
windows	83.90% <0.00%> (ø)

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