Add API stability check

[noahsmartin]

SPM has built in support for determining if a change breaks the public API of a framework using swift package diagnose-api-breaking-changes However I couldn't get this to work with a prebuilt binary. Internally that command uses swift-api-digester which is not very documented but I found a few threads on like this one.

This PR runs swift-api-digester to get a report of anything that change in the API which may be a breaking change. This does not do any checking of the report to prevent any change from landing, it just generates the report so if anyone is interested they can look at it on their PRs. I think it's good to have running in main as a sanity check, and to ensure the processes used to generate the report doesn't break.

I stopped short of having a breaking diff fail the CI check for two reasons:

1. Sometimes we do want to merge breaking changes, for example a feature that we are still working on and isn't released yet. Also adding a new default parameter to a function is considered a breaking change. Although it requires re-building the app since the exported symbol did change, it is still source code compatible and this tool doesn't check for that.
2. A false sense of security. Not every breaking change is caught by this, for example this is a Swift only tool so it won't detect if you drop an @objc annotation.

You can see the results of running this in the CI check logs. Here's a diff with no breaking changes

/* Generic Signature Changes */
/* RawRepresentable Changes */
/* Removed Decls */
/* Moved Decls */
/* Renamed Decls */
/* Type Changes */
/* Decl Attribute changes */
/* Fixed-layout Type Changes */
/* Protocol Conformance Change */
/* Protocol Requirement Change */
/* Class Inheritance Change */
/* Others */

This only checks iOS, but we could add others if this turns out to be useful!

#skip-changelog

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.894%. Comparing base (63307ef) to head (6bd8203).
Report is 9 commits behind head on main.

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #5288       +/-   ##
=============================================
+ Coverage   92.801%   92.894%   +0.093%     
=============================================
  Files          688       688               
  Lines        86264     86300       +36     
  Branches     30089     31202     +1113     
=============================================
+ Hits         80054     80168      +114     
+ Misses        6113      6029       -84     
- Partials        97       103        +6     

Files with missing lines	Coverage Δ
...ift/Integrations/UserFeedback/SentryFeedback.swift	72.727% <100.000%> (ø)

... and 23 files with indirect coverage changes

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[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1226.69 ms	1246.80 ms	20.10 ms
Size	23.76 KiB	821.43 KiB	797.67 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
bfe863d	1223.19 ms	1236.23 ms	13.04 ms
d33f2c8	1233.67 ms	1246.92 ms	13.24 ms
ebfe678	1234.63 ms	1254.52 ms	19.89 ms
06548c0	1226.71 ms	1252.37 ms	25.66 ms
216bdf9	1193.69 ms	1217.90 ms	24.21 ms
154f795	1225.53 ms	1231.04 ms	5.51 ms
2095ae0	1238.20 ms	1251.37 ms	13.17 ms
27f970b	1234.21 ms	1243.98 ms	9.77 ms
bdd896e	1211.19 ms	1239.06 ms	27.87 ms
0589699	1233.49 ms	1249.09 ms	15.60 ms

App size

Revision	Plain	With Sentry	Diff
bfe863d	21.58 KiB	414.57 KiB	392.99 KiB
d33f2c8	22.31 KiB	820.52 KiB	798.20 KiB
ebfe678	22.31 KiB	775.27 KiB	752.95 KiB
06548c0	20.76 KiB	427.36 KiB	406.59 KiB
216bdf9	21.58 KiB	418.13 KiB	396.54 KiB
154f795	20.76 KiB	435.25 KiB	414.49 KiB
2095ae0	21.90 KiB	709.06 KiB	687.16 KiB
27f970b	21.58 KiB	706.97 KiB	685.39 KiB
bdd896e	22.31 KiB	780.75 KiB	758.43 KiB
0589699	21.58 KiB	656.60 KiB	635.02 KiB

[philipphofmann]

I stopped short of having a breaking diff fail the CI check for two reasons:
Sometimes we do want to merge breaking changes, for example a feature that we are still working on and isn't released yet. Also adding a new default parameter to a function is considered a breaking change. Although it requires re-building the app since the exported symbol did change, it is still source code compatible and this tool doesn't check for that.
A false sense of security. Not every breaking change is caught by this, for example this is a Swift only tool so it won't detect if you drop an @objc annotation.
You can see the results of running this in the CI check logs. Here's a diff with no breaking changes

I think we can start with simply running this and see how it goes, but in the long run I think it would make sense that CI fails or adds a PR comment that it detected breaking changes. Otherwise, I think most people will ignore this check.