ref: rename SentryProfiler+Private.h to SentryProfilerState.h

[armcknight]

This has been throwing me off when trying to sort out some header imports. I don't think it should be called SentryProfiler+Private because it doesn't contain any interface extensions of SentryProfiler, but rather introduces only the new classes SentryProfilerState (and it's mutable counterpart).

#skip-changelog

[codecov]

Codecov Report

Merging #3124 (3373d60) into main (c2ec420) will increase coverage by 0.015%.
The diff coverage is n/a.

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #3124       +/-   ##
=============================================
+ Coverage   89.170%   89.185%   +0.015%     
=============================================
  Files          500       500               
  Lines        53908     53946       +38     
  Branches     19294     19311       +17     
=============================================
+ Hits         48070     48112       +42     
+ Misses        4985      4982        -3     
+ Partials       853       852        -1     

Impacted Files	Coverage Δ
Sources/Sentry/SentryProfiler.mm	83.595% <ø> (ø)
Tests/SentryProfilerTests/SentryProfilerTests.mm	98.728% <ø> (ø)

... and 13 files with indirect coverage changes

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[armcknight]

The lone test failure is either a flake or a very rare manifestation of the race condition being explored for #3090; in either case it doesn't have bearing on the changes in this PR so I'm not going to bother rerunning.