fix: Use UInts in envelope deserialization

[philipphofmann]

📜 Description

Use unsigned integers for the indexes for accessing envelope data to eliminate the risk of negative indices.

💡 Motivation and Context

Brought up as a nitpick by one of our customers, and it makes sense.

💚 How did you test it?

CI still green.

📝 Checklist

You have to check all boxes before merging:

• I reviewed the submitted code.
• 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.
• 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.

🔮 Next steps

[github-actions]

🚨 Detected changes in high risk code 🚨

High-risk code can easily blow up and is hard to test. We had severe bugs in the past. Be extra careful when changing these files, and have an extra careful look at these:

• Sources/Sentry/SentrySerialization.m

[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1241.29 ms	1264.02 ms	22.73 ms
Size	21.58 KiB	707.22 KiB	685.64 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
4bad5f9	1237.20 ms	1250.51 ms	13.31 ms
728804f	1235.26 ms	1254.20 ms	18.94 ms
861d361	1227.90 ms	1231.45 ms	3.55 ms
add8416	1270.72 ms	1300.38 ms	29.66 ms
af1f4dd	1225.39 ms	1245.48 ms	20.09 ms
ed49f0c	1245.67 ms	1261.15 ms	15.48 ms
7bc3c0d	1259.74 ms	1268.45 ms	8.71 ms
02a972c	1207.08 ms	1221.78 ms	14.70 ms
c59914b	1342.08 ms	1375.73 ms	33.65 ms
6943de0	1235.98 ms	1246.88 ms	10.90 ms

App size

Revision	Plain	With Sentry	Diff
4bad5f9	21.58 KiB	678.20 KiB	656.61 KiB
728804f	22.85 KiB	411.76 KiB	388.91 KiB
861d361	20.76 KiB	435.65 KiB	414.89 KiB
add8416	21.58 KiB	541.91 KiB	520.33 KiB
af1f4dd	22.85 KiB	414.71 KiB	391.86 KiB
ed49f0c	21.58 KiB	632.13 KiB	610.55 KiB
7bc3c0d	20.76 KiB	427.35 KiB	406.59 KiB
02a972c	22.85 KiB	413.42 KiB	390.57 KiB
c59914b	21.58 KiB	671.90 KiB	650.32 KiB
6943de0	20.76 KiB	393.33 KiB	372.57 KiB

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.345%. Comparing base (f273312) to head (49498c8).
Report is 8 commits behind head on main.

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #4441       +/-   ##
=============================================
+ Coverage   91.333%   91.345%   +0.011%     
=============================================
  Files          610       610               
  Lines        49927     49926        -1     
  Branches     18033     18042        +9     
=============================================
+ Hits         45600     45605        +5     
+ Misses        4235      4229        -6     
  Partials        92        92               

Files with missing lines	Coverage Δ
Sources/Sentry/SentrySerialization.m	98.360% <100.000%> (ø)

... and 5 files with indirect coverage changes

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