Add Task-level input sink to block cross-task tap pass-through

When there are TaskFragments that do not fill the entire Task, there
could be security concerns for touches passing through the unfilled area
in the Task and reaching the Task below. The risk could also happens in
adjacent TaskFragments.
Therefore, the change add a Task-level input sink to avoid the
cross-task touch pass through.

Bug: 490083213
Test: atest WmTests:TaskInputSinkTests
Flag: EXEMPT CVE_FIX
Cherrypick-From: https://googleplex-android-review.googlesource.com/q/commit:4373cf896dce49ba35ba2351d6bb974415bf9737
Cherrypick-From: https://googleplex-android-review.googlesource.com/q/commit:dfecc063216920aa833c86fbd415704d8aea0807
Merged-In: Icd0774a5ec642d57a06038e2635cd22ad9ab6cd6
Change-Id: Icd0774a5ec642d57a06038e2635cd22ad9ab6cd6