Add a test case to verify that multiple UIDs are

handled correctly in ConnectivityBlobStore.

Requires us to add a wrapper around
Binder.getCallingUid() in order to
mock having multiple calling apps.

Bug: 365543479
Flag: EXEMPT refactoring and test change
Test: atest ConnectivityBlobStoreTest
Change-Id: I451896d761b3526bcf5d76675ed1ed879cde04c2