[iOS] Several FullscreenVideoTextRecognition API tests are flaky failures

[whsieh]

d5d042e

[iOS] Several FullscreenVideoTextRecognition API tests are flaky failures
https://bugs.webkit.org/show_bug.cgi?id=243273
rdar://97567564

Reviewed by Tim Horton.

Address a couple sources of flaky crashes in these API tests on iOS:

1. It's possible for `-play` to trigger the video fullscreen presentation codepath (and thus, call
into `-presentViewController:animated:completion:` before the tests that call this method have
finished; in this scenario, the view controller presentation method isn't swizzled, so we end up
crashing in UIKit code due to lack of a UI application). Address this by pulling this logic out into
the common initializer of `FullscreenVideoTextRecognitionWebView` instead, to ensure that this call
into `UIViewController` remains swizzled throughout the entire duration of each test.

2. The swizzled implementation of `swizzledPresentViewController` are current unsafe, since nothing
guarantees that the completion handler is still alive by the time it is invoked on the next runloop
iteration. Address this by using `BlockPtr` to retain and release the completion block.

* Tools/TestWebKitAPI/Tests/WebKitCocoa/FullscreenVideoTextRecognition.mm:
(swizzledPresentViewController):
(-[FullscreenVideoTextRecognitionWebView initWithFrame:configuration:]):
(-[FullscreenVideoTextRecognitionWebView enterFullscreen]):

Canonical link: https://commits.webkit.org/252892@main

[whsieh]

Thanks for the review!

[webkit-commit-queue]

Committed 252892@main (d5d042e): https://commits.webkit.org/252892@main

Reviewed commits have been landed. Closing PR #2797 and removing active labels.