Fix not handled pointercancel event

[nianxy]

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Description

When I use the multi-touch gesture on a mobile device, there may be a 'pointercancel' event fired under some situations. In this situation, the Gesture instance is not disposed because the code is waiting for the 'pointerup' event, and the following events are all affected by the Gesture.

We can make the 'pointerup' event listener to also listen to the 'pointercancel' event, and I will try to commit a PR to fix this problem.

Reproduction steps

1. Try to use two fingers to pinch the workspace and hold the fingers on the screen
2. Try to fire a 'pointercancel' event, for example, move the two fingers very close
3. Release the fingers, and try to move the workspace by a finger, you can find that the moving action is abnormal

Stack trace

None

Screenshots

VID_20250723_113041.mp4

Browsers

No response

[maribethb]

Easy-ish steps to reproduce to get a pointercancel event going:

1. Use a real touch device such as an iphone
2. Touch and drag a block
3. While keeping a finger on the block, mid-drag, use the physical button to lock the iphone screen
4. Let go of the screen while the phone is locked
5. Unlock the phone
6. Try to interact with the blockly workspace again

If this bug is occurring, the gesture will be broken as in the video. The block thinks it's still being dragged and there's no way to end the drag. Touching the screen just makes the block jump around.

If this bug is fixed, the gesture will have been ended when the phone was locked, and when you resume interaction, everything works as expected.

I was also able to test this by resting my palm on my phone and getting palm rejection to kick in, but it can be hard to tell if the bug isn't occurring or if palm rejection hasn't kicked in. Locking the device was a sure way to get a pointercancel.