[Expandable] Add isAttached check in onGloballyPositioned

This change fixes a crash that can occur during an expandable animation.
There is a potential crash when onGloballyPositioned is called after a
composable has been detached or before it is attached from the UI
hierarchy. The fix adds a check to ensure the composable is still
attached before performing layout operations.

Bug: 405199654
Test: n/a because i couldn't reproduce the crash.
Flag: EXEMPT crash fix.
Change-Id: Ib5041f190d3326e9cba15126b60871f55a52fd27