ref-filter: move code from 'for-each-ref'

ref-filter: move code from 'for-each-ref'

Move most of the code from 'for-each-ref' to 'ref-filter' to make
it publicly available to other commands, this is to unify the code
of 'tag -l', 'branch -l' and 'for-each-ref' so that they can share
their implementations with each other.

Add 'ref-filter' to the Makefile, this completes the movement of code
from 'for-each-ref' to 'ref-filter'.

Mentored-by: Christian Couder <redacted>
Mentored-by: Matthieu Moy <redacted>
Signed-off-by: Karthik Nayak <redacted>
Reviewed-by: Matthieu Moy <redacted>
Signed-off-by: Junio C Hamano <redacted>