feat(profiling): add API to SentrySDK to start/stop a continuous profiling session

[armcknight]

And thread it through to a stub for new implementation for the continuous profiler.

Add a check for where the legacy profiler is started from SentryTracer for the new feature flag.

TODO

- [ ] Haven't decided what to do yet with the launch profiler; I think it will also need the feature flag at the spots that automatically stop the tracer managing it, so it is left running throughout the app session or until SentrySDK.stopProfiler is called.
- [ ] just learned (April 5) that we will automatically start profiling from SentrySDK.startWithOptions (if launch profiling isn't enabled) which will respect profiles sample rate, so this needs to be added here or in a subsequent PR
I am just going to leave this PR as the stub for the new continuous profiler and leave it to a future PR to deliver the implementation of automatic/manual start/stop.

#skip-changelog

for #3555

[github-actions]

	Messages
📖	Do not forget to update Sentry-docs with your feature once the pull request gets approved.

Generated by 🚫 dangerJS against e74d85b

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 12 lines in your changes are missing coverage. Please review.

Project coverage is 90.627%. Comparing base (3de9971) to head (e74d85b).
Report is 6 commits behind head on main.

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #3834       +/-   ##
=============================================
- Coverage   90.957%   90.627%   -0.331%     
=============================================
  Files          560       579       +19     
  Lines        44271     45240      +969     
  Branches     15776     16098      +322     
=============================================
+ Hits         40268     41000      +732     
- Misses        3822      4060      +238     
+ Partials       181       180        -1     

Files	Coverage Δ
Sources/Sentry/SentryProfiler.mm	85.333% <ø> (ø)
Sources/Sentry/SentryTracer.m	96.658% <ø> (ø)
...ources/Sentry/Profiling/SentryContinuousProfiler.m	0.000% <0.000%> (ø)
Sources/Sentry/SentrySDK.m	86.470% <0.000%> (-5.405%)	⬇️

... and 40 files with indirect coverage changes

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[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1245.19 ms	1261.57 ms	16.38 ms
Size	21.58 KiB	612.82 KiB	591.24 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
4b1a58e	1237.39 ms	1265.63 ms	28.23 ms
d10ae0c	1250.02 ms	1253.74 ms	3.72 ms
0559a8f	1239.78 ms	1252.60 ms	12.83 ms
dcec216	1238.94 ms	1261.06 ms	22.12 ms
4bca912	1252.42 ms	1260.06 ms	7.64 ms
42ef6ba	1234.35 ms	1252.29 ms	17.94 ms
ca91a5c	1234.53 ms	1249.86 ms	15.33 ms
aeec206	1211.31 ms	1229.18 ms	17.87 ms
83887af	1196.94 ms	1206.82 ms	9.88 ms
4259afd	1222.12 ms	1249.74 ms	27.62 ms

App size

Revision	Plain	With Sentry	Diff
4b1a58e	22.85 KiB	407.02 KiB	384.17 KiB
d10ae0c	20.76 KiB	419.86 KiB	399.10 KiB
0559a8f	21.58 KiB	419.81 KiB	398.23 KiB
dcec216	20.76 KiB	432.88 KiB	412.11 KiB
4bca912	22.85 KiB	411.14 KiB	388.29 KiB
42ef6ba	21.58 KiB	417.86 KiB	396.28 KiB
ca91a5c	22.84 KiB	403.19 KiB	380.34 KiB
aeec206	20.76 KiB	434.88 KiB	414.12 KiB
83887af	21.58 KiB	419.64 KiB	398.06 KiB
4259afd	20.76 KiB	419.70 KiB	398.94 KiB

Previous results on branch: armcknight/feat/3555-continuous-profiling/3-new-public-api

Startup times

Revision	Plain	With Sentry	Diff
77de107	1234.90 ms	1246.52 ms	11.62 ms

App size

Revision	Plain	With Sentry	Diff
77de107	21.58 KiB	574.89 KiB	553.31 KiB

[philipphofmann]

LGTM