ref(continuous profiling): clarify initial options values

[armcknight]

Disambiguated the initial value for profilesSampleRate and the default value to revert to in case of invalid configuration. Clarified the meaning of these in a few spots, including a new test.

See also https://www.notion.so/sentry/Continuous-Profiling-SDK-Options-46f8f4ce691a4fedbcc39c7f1e1e740e?pvs=4

#skip-changelog

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 4 lines in your changes missing coverage. Please review.

Project coverage is 91.381%. Comparing base (19b93f9) to head (c078a67).

Files	Patch %	Lines
Sources/Sentry/SentrySDK.m	50.000%	4 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #4216       +/-   ##
=============================================
- Coverage   91.404%   91.381%   -0.024%     
=============================================
  Files          611       611               
  Lines        49051     49067       +16     
  Branches     17707     17712        +5     
=============================================
+ Hits         44835     44838        +3     
- Misses        4122      4135       +13     
  Partials        94        94               

Files	Coverage Δ
Sources/Sentry/SentryOptions.m	99.259% <100.000%> (ø)
Sources/Sentry/include/SentryInternalDefines.h	72.413% <100.000%> (+0.985%)	⬆️
Tests/SentryTests/SentryOptionsTest.m	97.899% <100.000%> (+0.029%)	⬆️
Sources/Sentry/SentrySDK.m	88.700% <50.000%> (-0.895%)	⬇️

... and 5 files with indirect coverage changes

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[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1230.18 ms	1253.55 ms	23.37 ms
Size	21.58 KiB	694.49 KiB	672.90 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
d760c3f	1228.58 ms	1246.22 ms	17.64 ms
3f74b8f	1229.90 ms	1249.42 ms	19.52 ms
983de17	1260.57 ms	1263.68 ms	3.11 ms
5d6ce0e	1206.72 ms	1228.67 ms	21.95 ms
bd2afa6	1192.31 ms	1210.37 ms	18.05 ms
1e065bc	1239.69 ms	1258.18 ms	18.49 ms
3478fc5	1237.94 ms	1251.13 ms	13.19 ms
3297d6e	1196.08 ms	1205.43 ms	9.35 ms
5be7a7c	1223.25 ms	1237.12 ms	13.87 ms
a176fc4	1250.29 ms	1257.88 ms	7.59 ms

App size

Revision	Plain	With Sentry	Diff
d760c3f	22.84 KiB	403.17 KiB	380.33 KiB
3f74b8f	21.58 KiB	418.78 KiB	397.20 KiB
983de17	22.84 KiB	403.19 KiB	380.34 KiB
5d6ce0e	22.85 KiB	405.38 KiB	382.53 KiB
bd2afa6	20.76 KiB	420.55 KiB	399.79 KiB
1e065bc	20.76 KiB	425.78 KiB	405.01 KiB
3478fc5	21.58 KiB	654.59 KiB	633.01 KiB
3297d6e	21.58 KiB	418.44 KiB	396.86 KiB
5be7a7c	21.58 KiB	671.89 KiB	650.31 KiB
a176fc4	22.84 KiB	403.24 KiB	380.39 KiB