Use a non-null package name when creating a ComponentName

While we shouldn't be able to use a null value for a ComponentName
(according to the comments in the code at least), it seems our test is
able to make make one with a mock context that doesn't have a mocked
value returned for getPackage(). This has downstream effects if someone
ever calls equals() with our ComponentName, which does not null check
the package name.

This change adds a simple mocked value for getPackageName().

Tag: #refactor
Bug: 231246591
Test: atest HfpClientDeviceBlockTest
Merged-In: Icedf4c11efd242d925c0c8d993d9706882df54c2
Change-Id: Icedf4c11efd242d925c0c8d993d9706882df54c2