Always run the intent filter verifier in USER_SYSTEM

The temporary whitelisting of the intent filter verifier was not
taking effect when an app install was applied to all users, because
the USER_ALL userid argument was not applicable downstream in the
whitelist-package-within-user code flow.  The verifier is located
explicitly in the system user anyway; we do not need to try to
launch or whitelist it in a per-target-user manner.

In addition, the whitelisting operation is now synchronous to avoid
any slight race between delivery of the verification broadcast and
application of the new whitelist state.

Bug 62814249
Test: manual

Change-Id: I051277dad6c541d0aa6bcdd824ad3cce4b20b269