Move push matching and reporting logic into transport.c

Move push matching and reporting logic into transport.c

For native-protocol pushes (and other protocols as they are converted
to the new method), this moves the refspec match, tracking update, and
report message out of send-pack() and into transport_push(), where it
can be shared completely with other protocols. This also makes fetch
and push more similar in terms of what code is in what file.

Signed-off-by: Daniel Barkalow <redacted>
Signed-off-by: Junio C Hamano <redacted>