Fix LauncherProxyServiceTest for HSUM

The service was not bound in hsum mode, but for test purposes the fact the device is hsum is irrelevant.

Now we're injecting a class that tells whether the device is hsum, and faking it in tests.

Bug: 411363072
Test: LauncherProxyServiceTest
Flag: NONE - small bugfix
Change-Id: I715f76cba01e507bdf41017410965cd42bc61547