Clean up SMS filter handling.

Define an interface for filters and perform filtering as a generic
iteration over the list of filters. Lower code duplication by
providing the list of remaining filters to each filter, allowing
an asynchronous filter (like the carrier filter) to invoke any.
remaining filters generically.

This should mostly be a no-op. However, there is one small behavioral
change - the MissedIncomingCallSmsFilter will now be invoked for
messages which are passed through and not dropped by the carrier SMS
filter and the visual voicemail SMS filter. This seems like it should
be the case for consistency.

Also allow overriding SMS filters for testing and add unit tests to
exercise filter invocation.

This is a precursor CL to one which will pass SMSes from blocked
numbers through the filters to prevent vital system messages from
being blocked.

Bug: 136262737
Test: atest GsmInboundSmsHandlerTest
Change-Id: I280d8e4c0847bf261e0497f95231a5063dfa025f
Merged-In: I280d8e4c0847bf261e0497f95231a5063dfa025f