Use correct API to get calling package name in CredentialStorage

Activity.getCallingPackage() does not always return the package
name of the actual calling app. getLaunchedFromPackage() should
be used instead.

Bug: 389681530
Test: manual
Flag: EXEMPT bugfix
(cherry picked from commit 70bd3efe)
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:5a82b21528b9c2a2340b3e18b40ac737dd23a658)
Merged-In: Ibdbc45e53f4aa46fae79fa234705b3735bfda4cd
Change-Id: Ibdbc45e53f4aa46fae79fa234705b3735bfda4cd