Report Flutter framework feature flags

[ueman]

:scroll: Description

There's a Flutter framework (draft) PR that adds feature flags to Flutter itself. This PR supports that

:bulb: Motivation and Context

I want know whether a specific build used one of the feature flags.

:green_heart: How did you test it?

I didn't. I'm not really sure how to even test this with a non-flaky test.

:pencil: Checklist

• [x] I reviewed submitted code
• [x] I added tests to verify changes
• [x] No new PII added or SDK only sends newly added PII if sendDefaultPii is enabled
• [x] I updated the docs if needed
• [x] All tests passing
• [x] No breaking changes

:crystal_ball: Next steps

I'll keep this a draft until the linked PR is merged for some time. Afterwards this PR can be landed.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 92.85714% with 1 line in your changes missing coverage. Please review.

Project coverage is 88.89%. Comparing base (81f83eb) to head (31bf545). Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...ns/flutter_framework_feature_flag_integration.dart	92.30%	1 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2991      +/-   ##
==========================================
+ Coverage   87.74%   88.89%   +1.15%     
==========================================
  Files         286       97     -189     
  Lines        9719     3522    -6197     
==========================================
- Hits         8528     3131    -5397     
+ Misses       1191      391     -800     

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[ueman]

I would still wait with merging this PR until the linked PR is merged

[ueman]

@buenaflor The dependent PR in the Flutter framework has landed, so I would say we can go ahead and merge this PR

[buenaflor]

@ueman sounds good

also does the cursor review make sense? if not we can just ignore it

[ueman]

I assume those cases should not happen since the flags are supplied by the flutter tool and not user generated, but I added code and tests for them anyway