Add type annotation to the phase parameter.

This commit adds the `@LaunchParamsModifier.Phase` annotation to the
phase parameters. This prevents accidental passing of invalid phase
values and improves readability.

BUG: 387193964
Flag: EXEMPT refactor
Test: Local build
Change-Id: Ie6b3c3f4b75a813014e648e7c3daafc0241b113e