Move utilities in LPMUtils to LPUtil

I chose LaunchParamsUtil over LaunchParamsModifierUtility

1. For its simpler name;
2. For its longer code history; and
3. To keep the original authors of utility functions in git history.

Also made a few adjustments in tests to improve readability.

Bug: 340460999
Bug: 340172101
Bug: 340172030
Test: atest WmTests:DesktopModeLaunchParamsModifierTests
Test: atest WmTests:TaskLaunchParamsModifierTests
Change-Id: I918b5a82a23db8a370ffcfc8fc9b094027b00b7c