Add UID in AppInfo.

Create a reverse hashmap of PackageUserKey to Uid in AllAppsStore for
faster lookup of uid based on packageName and userHandle.

Log Uid in Impression Logging.

Bug: 282849559
Test: Manual. See various usecases documented in http://shortn/_UcvAYOmLIP
Flag: NA

Change-Id: I416426214f6b6efc45f7d4c0433bbbfca9056adf