Fix CredentialManager for use_resource_processor: true

CredentialManagerShared was using the same Android package name as
CredentialManager-handheld, which caused the R classes to be shadowed
when use_resource_processor: true is enabled.  Use a unique Android
package for CredentialManagerShared.

Bug: 294256649
Test: m javac-check
Change-Id: I07fea5636c6ca8f6752a11ca230e04ee172b140b