ref: Remove internal init of AppStartMeasurement

[philipphofmann]

SentryAppStartMeasurement is only plublic for hybrid SDKs since #2458. Therefore, we can remove the deprecated init method.

#skip-changelog

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (3d3a411) 89.237% compared to head (6749d0f) 89.250%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #3525       +/-   ##
=============================================
+ Coverage   89.237%   89.250%   +0.012%     
=============================================
  Files          528       528               
  Lines        57572     57575        +3     
  Branches     20633     20645       +12     
=============================================
+ Hits         51376     51386       +10     
+ Misses        5287      5276       -11     
- Partials       909       913        +4     

Files	Coverage Δ
Sources/Sentry/SentryAppStartMeasurement.m	100.000% <ø> (+43.478%)	⬆️

... and 13 files with indirect coverage changes

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[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1213.63 ms	1215.67 ms	2.03 ms
Size	21.58 KiB	418.44 KiB	396.86 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
98a8c16	1234.69 ms	1265.02 ms	30.33 ms
591a01b	1197.94 ms	1222.53 ms	24.59 ms
98713e6	1211.48 ms	1244.42 ms	32.94 ms
01a28a9	1237.24 ms	1253.24 ms	16.00 ms
dd0557f	1246.31 ms	1258.46 ms	12.15 ms
2a894d5	1211.02 ms	1236.72 ms	25.70 ms
f576153	1217.17 ms	1225.06 ms	7.89 ms
17afc4b	1228.94 ms	1251.10 ms	22.16 ms
1bf8571	1250.96 ms	1255.36 ms	4.40 ms
c40576a	1202.45 ms	1224.60 ms	22.15 ms

App size

Revision	Plain	With Sentry	Diff
98a8c16	20.76 KiB	431.00 KiB	410.24 KiB
591a01b	22.84 KiB	401.67 KiB	378.83 KiB
98713e6	20.76 KiB	435.22 KiB	414.46 KiB
01a28a9	22.85 KiB	405.39 KiB	382.54 KiB
dd0557f	22.85 KiB	411.75 KiB	388.90 KiB
2a894d5	21.58 KiB	414.57 KiB	392.99 KiB
f576153	20.76 KiB	425.77 KiB	405.01 KiB
17afc4b	20.76 KiB	436.25 KiB	415.49 KiB
1bf8571	20.76 KiB	437.12 KiB	416.36 KiB
c40576a	22.85 KiB	407.63 KiB	384.78 KiB