pack-bitmap: enable lookup tables by default, misc. cleanups

This is a short series I extracted from a larger topic on reusing "external"[^1] deltas during verbatim pack reuse.

As part of performance-testing that series, I realized that bitmap lookup tables are not written by default. Since it has been a significant period of time since their introduction, the first patch of this series makes writing the lookup table extension the default behavior. This is:

* pack-bitmap: write lookup table extension by default

The next three patches clean up some t/perf scripts that were redundant now that lookup tables are the default behavior. Those are:

* p5312: removed duplicate performance test script
* t/perf: avoid testing bitmaps without lookup table
* t/perf/lib-bitmap.sh: avoid test_perf during setup

Thanks in advance for your review :-).

[^1]: The term I'm using to describe delta/base pairs which either (a) are represented from different packs in a MIDX bitmap, or (b) the client is known to already have the base.

Taylor Blau (4):
pack-bitmap: write lookup table extension by default
p5312: removed duplicate performance test script t/perf: avoid testing bitmaps without lookup table t/perf/lib-bitmap.sh: avoid test_perf during setup

 Documentation/config/pack.adoc       |   2 +-
 builtin/multi-pack-index.c           |   1 +
 builtin/pack-objects.c               |   2 +-
 t/perf/lib-bitmap.sh                 |   2 +-
 t/perf/p5310-pack-bitmaps.sh         |  47 +++++-------
 t/perf/p5311-pack-bitmaps-fetch.sh   |  76 +++++++++----------
 t/perf/p5312-pack-bitmaps-revs.sh    |  34 ---------
 t/perf/p5326-multi-pack-bitmaps.sh   | 107 ++++++++++++---------------
 t/perf/p5333-pseudo-merge-bitmaps.sh |   1 -
 9 files changed, 106 insertions(+), 166 deletions(-)
 delete mode 100755 t/perf/p5312-pack-bitmaps-revs.sh

base-commit: c152ae3ef50dc7bbbf5089571df5bba404a96e0d

2.49.0.226.g0e6cae136d