Fix wrong ime parent in embedded activity

We have CL[1] to polish the ime transition. But in
ActivityEmbedding, the ime layering target may higher
than input target. And the ime parent didn't be updated
since input target and layering target are unsync.

Update ime parent for this case.

[1]: I332c0e4fff62df5d7b793eda2767bb58fe85a938

Bug: 260387203
Test: Manual test with test apk in the bug
Test: atest TaskFragmentTest#testUpdateImeParentForActivityEmbedding
Change-Id: I78c82a0677d2ab7a1e247e91e5dfa1e5235e95bb