Rename tests in ComponentCallerTest and fix potential flakiness

This change does the following:
1. Renames existing tests to reflect the tested caller type, which is
   the initial caller. The renaming is also applied to comments and
   test activities.
2. Fixes potential flakiness of using ComponentCallerTest$TestProvider's
   base content URI by instead using a content URI with a unique
   appended ID. The contentUriViaGrant test grants a specific permission
   to the helper app, which can affect the result of the
   throwsIfCallerOfApiDoesNotHaveTheSameAccessToContentUri test that
   uses that content URI assuming the helper app doesn't have permission
   to it.

Bug: 293467489
Test: atest CtsAndroidAppTestCases:android.app.cts.ComponentCallerTest
Change-Id: I69157a3991aab6b0eddcc3aa6941f307e0869c61