remove download scripts, consolidate into script

most of them were just calling the gitclone script,
so remove them.

the grub script was treating gnulib as a dependency.
i've now added the ability to grab 1 dependency, in
the gitclone script (it should be expanded later to
support multiple dependencies)

the gitclone script has been renamed to "fetch".
the "fetch_trees" script does more or less the same
thing, but calls "fetch" and handles multiple revisions
if a project needs that

this is more efficient, and slightly reduces the code
size of lbmk!

Signed-off-by: Leah Rowe <leah@libreboot.org>

Makefile

@@ -25,7 +25,7 @@
 
 .POSIX:
 
-#.PHONY: all check download modules ich9m-descriptors payloads roms release \
+#.PHONY: all check modules ich9m-descriptors payloads roms release \
 #	clean crossgcc-clean install-dependencies-ubuntu \
 #	install-dependencies-debian install-dependencies-arch \
 #	install-dependencies-void install-dependencies-fedora38 \
@@ -33,9 +33,6 @@
 
 all: roms
 
-download:
-	./download all
-
 modules:
 	./build module all