[Role Logic Move] Lift user from Permissions::getPermissionFlags

This change modifies the following (private) methods:

- Permissions::getPermissionFlags[AsUser]
- Permissions::isPermissionFixed[AsUser]
- Permissions::isPermissionGrantedByDefault[AsUser]

...by making them multi-user aware. I.e., lift any references to
Process.myUserHandle() out of them into method arguments.

Bug: 302563690
Test: atest CtsRoleTestCases
Change-Id: Ib80da2bdedfc3e019fa786276c183d9060b6b737