transport: rename negotiation_tips

transport: rename negotiation_tips

The previous change added the --negotiation-restrict synonym for the
--negotiation-tip option for 'git fetch'. In anticipation of adding a new
option that behaves similarly but with distinct changes to its behavior,
rename the internal representation of this data from 'negotiation_tips' to
'negotiation_restrict_tips'.

The 'tips' part is kept because this is an oid_array in the transport layer.
This requires the builtin to handle parsing refs into collections of oids so
the transport layer can handle this cleaner form of the data.

Also update the string_list used to store the inputs from command-line
options.

Reviewed-by: Matthew John Cheetham <mjcheetham@outlook.com>
Signed-off-by: Derrick Stolee <stolee@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>