[ios][pv] Reland platform view hitTest approach (again)

[hellohuanlin]

This PR tries to reland the previous PR: #183484. Refer to it for more details.

What happened to the previous PR?

2 tests from ios_platform_view_ui_test failed due to edge swipe gesture (https://www.youtube.com/watch?v=MVO5b0eEdw8). Cupertino puts a gesture listener on left edge of screen. When tapping there, the hitTest logic returns the gesture listener as the first hit (instead of our platform view), hence blocking the platform view.

Why we didn't find this issue before?

Because it only happen to iPhone, but I use iPad for testing.

What's the fix?

In flutter, hitTest returns a list of all targets that should be hit tested. So instead of checking if the first hit is the platform view, we check if the result contains any platform view.

I have also created a UIKit app, and verified that the expected behavior is that platform view should still receive touch even if swipe edge back gesture is recognized.

A key info is that during Flutter's hitTest operation, the result list will not contain a target if it is blocked by another target in front (e.g. context menu covering a platform view).

If there are multiple platform views, that's fine too, because UIKit itself will perform hitTest which finds the correct touch intercepting view, which sends the request to framework.

List which issues are fixed by this PR. You must list at least one issue. An issue is not required if the PR fixes something trivial like a typo.

Fixes#179916
Fixes#175099

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[hellohuanlin]

Will revert this after verifying it worked on CI.

[gemini-code-assist]

Code Review

This pull request implements a synchronous hit-testing mechanism for iOS platform views, enabling the Flutter framework to decide whether a touch should be delivered to a native view or blocked by overlapping Flutter widgets. Key changes include adding an onHitTest callback to the PlatformDispatcher, introducing the NativeHitTestTarget mixin for render objects, and exposing a new gestureBlockingPolicy for UiKitView. Feedback suggests optimizing the hitTest:withEvent: override in FlutterTouchInterceptingView by checking view visibility and interaction status before performing the framework hit test.

[hellohuanlin]

@loic-sharma@chunhtai@vashworth FYI the first 6 commits are exactly the same as previous PR landed. I added 2 new commits:

1. the hitTest logic change which fixes the issue
2. renamed isPlatformView to hasPlatformView

[hellohuanlin]

Mac_ios native_platform_view_ui_tests_iosSuccessful in 9m

Confirmed the fix passes the test. Will disable the pre-submit

[chunhtai]

LGTM

[chenenyu]

Hello, when will this pr be merged into the stable branch?

[thamtumeoden13]

Thanks for merging this fix.
Could you share whether PR #185126 is planned for an upcoming stable release (or cherry-pick), and if so, which version?