Sanitize window private flags based on caller permissions.

Introduces `sanitizePrivateFlags` to check if the calling application has the necessary permissions to set certain `LayoutParams.privateFlags`. Specifically, `PRIVATE_FLAG_IS_ROUNDED_CORNERS_OVERLAY` and `PRIVATE_FLAG_TRUSTED_OVERLAY` require `INTERNAL_SYSTEM_WINDOW`, and `PRIVATE_FLAG_INTERCEPT_GLOBAL_DRAG_AND_DROP` requires `MANAGE_ACTIVITY_TASKS`. These flags are removed if the caller lacks the required permissions during window relayout.

Bug: 406243581
Test: atest WindowManagerServiceTests
Flag: EXEMPT bug fix

Change-Id: I4fdf2152f06082e13690e7f5b628e0ca0acdff84