bisect: simplify the addition of new bisect terms

bisect: simplify the addition of new bisect terms

We create a file BISECT_TERMS in the repository .git to be read during a
bisection. There's no user-interface yet, but "git bisect" works if terms
other than old/new or bad/good are set in .git/BISECT_TERMS. The
fonctions to be changed if we add new terms are quite few.

In git-bisect.sh:
	check_and_set_terms
	bisect_voc

Co-authored-by: Louis Stuber <redacted>
Tweaked-by: Matthieu Moy <redacted>
Signed-off-by: Antoine Delaite <redacted>
Signed-off-by: Louis Stuber <redacted>
Signed-off-by: Valentin Duperray <redacted>
Signed-off-by: Franck Jonas <redacted>
Signed-off-by: Lucien Kong <redacted>
Signed-off-by: Thomas Nguy <redacted>
Signed-off-by: Huynh Khoi Nguyen Nguyen <redacted>
Signed-off-by: Matthieu Moy <redacted>
Signed-off-by: Junio C Hamano <redacted>