fix: Wrong Frame Delay when becoming active

[philipphofmann]

📜 Description

The SDK reported false frame delay statistics when it moved from the background to the foreground, which also led to falsely reported app hangs.

After merging this PR, I'm going to open up the same PR to v8 and release a hotfix.

💡 Motivation and Context

Fixes GH-6345

💚 How did you test it?

I failed to reproduce the exact problem the user described in GH-6345, and so did the user. I noticed that the SDK calculated wrong frame delay numbers when moving from the background to the foreground, so I added unit tests for these scenarios.

📝 Checklist

You have to check all boxes before merging:

• I added tests to verify the changes.
• No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
• I updated the docs if needed.
• I updated the wizard if needed.
• Review from the native team if needed.
• No breaking change or entry added to the changelog.
• No breaking change for hybrid SDKs or communicated to hybrid SDKs.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.764%. Comparing base (d72784d) to head (9ed9c46).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #6381       +/-   ##
=============================================
+ Coverage   86.744%   86.764%   +0.020%     
=============================================
  Files          439       439               
  Lines        37238     37242        +4     
  Branches     17368     17365        -3     
=============================================
+ Hits         32302     32313       +11     
+ Misses        4891      4886        -5     
+ Partials        45        43        -2     

Files with missing lines	Coverage Δ
Sources/Sentry/SentryDelayedFramesTracker.m	96.527% <100.000%> (+0.099%)	⬆️
Sources/Sentry/SentryFramesTracker.m	100.000% <100.000%> (ø)

... and 9 files with indirect coverage changes

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update d72784d...9ed9c46. Read the comment docs.

[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1206.02 ms	1239.04 ms	33.02 ms
Size	23.75 KiB	987.93 KiB	964.19 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
a4c5ddc	1239.61 ms	1266.41 ms	26.80 ms
08fc5f9	1237.84 ms	1270.06 ms	32.23 ms
f5666e7	1227.08 ms	1260.18 ms	33.10 ms
7908e84	1224.33 ms	1246.39 ms	22.06 ms
d3f650a	1225.45 ms	1241.86 ms	16.41 ms
c122943	1210.94 ms	1233.78 ms	22.84 ms
cc7f629	1226.00 ms	1245.51 ms	19.51 ms
d66f082	1227.08 ms	1247.04 ms	19.96 ms
04ff3ec	1220.71 ms	1253.86 ms	33.15 ms
7b3399c	1193.35 ms	1227.38 ms	34.03 ms

App size

Revision	Plain	With Sentry	Diff
a4c5ddc	23.75 KiB	977.30 KiB	953.55 KiB
08fc5f9	23.75 KiB	995.43 KiB	971.68 KiB
f5666e7	23.75 KiB	963.18 KiB	939.43 KiB
7908e84	23.74 KiB	872.75 KiB	849.00 KiB
d3f650a	23.75 KiB	902.48 KiB	878.73 KiB
c122943	23.74 KiB	926.65 KiB	902.90 KiB
cc7f629	23.75 KiB	878.48 KiB	854.73 KiB
d66f082	23.75 KiB	928.85 KiB	905.10 KiB
04ff3ec	23.75 KiB	880.26 KiB	856.52 KiB
7b3399c	23.75 KiB	946.68 KiB	922.94 KiB

Previous results on branch: fix/frames-delay-from-background

Startup times

Revision	Plain	With Sentry	Diff
c228d62	1227.12 ms	1267.90 ms	40.78 ms
780d634	1225.86 ms	1256.44 ms	30.58 ms
bce284a	1219.55 ms	1259.43 ms	39.88 ms

App size

Revision	Plain	With Sentry	Diff
c228d62	23.74 KiB	987.03 KiB	963.29 KiB
780d634	23.74 KiB	986.69 KiB	962.94 KiB
bce284a	23.75 KiB	987.97 KiB	964.23 KiB