pack-bitmap-write: learn pack.writeBitmapLookupTable and add tests
Teach Git to provide a way for users to enable/disable bitmap lookup
table extension by providing a config option named 'writeBitmapLookupTable'.
Default is false.
Also add test to verify writting of lookup table.
Mentored-by: Taylor Blau <me@ttaylorr.com> Co-Mentored-by: Kaartic Sivaraam <kaartic.sivaraam@gmail.com> Co-Authored-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Abhradeep Chakraborty <chakrabortyabhradeep79@gmail.com> Reviewed-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>