refactor duplicated code in builtin-send-pack.c and transport.c

The following functions are (almost) identical:

verify_remote_names
update_tracking_ref
refs_pushed
print_push_status

Move common versions of these functions to transport.c and rename
them, as suggested by Jeff King and Junio C Hamano.

These functions have been removed entirely from builtin-send-pack.c,
since they are only used internally by print_push_status():

print_ref_status
status_abbrev
print_ok_ref_status
print_one_push_status

Also, move #define SUMMARY_WIDTH to transport.h and rename it
TRANSPORT_SUMMARY_WIDTH as it is used in builtin-fetch.c and
transport.c

Signed-off-by: Michael Lukashov <michael.lukashov@gmail.com>
Acked-by: Tay Ray Chuan <rctay89@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>