pathspec: rename per-item field has_wildcard to use_wildcard

pathspec: rename per-item field has_wildcard to use_wildcard

As the point of the last change is to allow use of strings as
literals no matter what characters are in them, "has_wildcard"
does not match what we use this field for anymore.

It is used to decide if the wildcard matching should be used, so
rename it to match the usage better.

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