[ios][platform_view]force reset forwarding recognizer state when its stuck

[hellohuanlin]

This PR force reset forwarding recognizer state when it's stuck at failed state, by recreating the recognizer (we are not able to reset the state back to possible - it has to be reset by UIKit).

This is a tricky one since pencil and finger triggers exactly the same callbacks. It turns out that when pencil is involved after finger interaction, the platform view's "forwarding" gesture recognizer is stuck at failed state. This seems to be an iOS bug, because according to the API doc, it should be reset back to "possible" state:

No action message is sent and the gesture recognizer is reset to UIGestureRecognizerStatePossible.

However, when iPad pencil is involved, the state is not reset. I tried to KVO the state property, and wasn't able to capture the change. This means the state change very likely happened internally within the recognizer via the backing ivar of the state property.

Fixes https://github.com/flutter/flutter/issues/136244

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• [x] I listed at least one issue that this PR fixes in the description above.
• [x] I added new tests to check the change I am making or feature I am adding, or the PR is test-exempt. See testing the engine for instructions on writing and running engine tests.
• [x] I updated/added relevant documentation (doc comments with ///).
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• [x] All existing and new tests are passing.

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[flutter-dashboard[bot]]

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[hellohuanlin]

Tested the demo app from github issue and confirmed it's working. I will do more testing before landing it.

[hellohuanlin]

Verified both google map and web view plugin example apps still work as expected.

[polina-c]

@tdevaux confirmed this fixes the issue

[hellohuanlin]

I don't know if change would impact it, but can you confirm the totally-not-running-anywhere iPad gesture tests still pass? https://github.com/flutter/engine/blob/4e6405e2a89fa8fda2c0e7017ddcd8b39d7b3052/testing/scenario_app/ios/Scenarios/ScenariosUITests/iPadGestureTests.m

I got all of them failed with main branch on simulator. Let me try physical devices.

[jmagman]

I got all of them failed with main branch on simulator. Let me try physical devices.

Don't worry about it, we can investigate later and get them passing and running somewhere. Let's merge this! 🙂

[hellohuanlin]

I was able to run on device and got the same failure as simulator. Filed https://github.com/flutter/flutter/issues/157454

[auto-submit[bot]]

auto label is removed for flutter/engine/55958, due to - The status or check suite Mac mac_unopt has failed. Please fix the issues identified (or deflake) before re-applying this label.