t7900: untangle test dependencies

Untangle test dependencies so that all tests only need setup tests to have been run.

For example:

```
./t7900-maintenance.sh --run=setup,31
```

Test with:

```
#!/bin/sh
cd t
# Every test run together with `setup` should pass
for i in $(seq 1 42)
do
    ./t7900-maintenance.sh --quiet --run=setup,$i || return 1
done &&
# Whole test suite should pass
./t7900-maintenance.sh --quiet &&
# The tests that used to depend on each other should still pass
# when run together
./t7900-maintenance.sh --quiet --run=setup,30,31 &&
./t7900-maintenance.sh --quiet --run=setup,11,12 &&
./t7900-maintenance.sh --quiet --run=setup,3,19 &&
./t7900-maintenance.sh --quiet --run=setup,23,24 &&
./t7900-maintenance.sh --quiet --run=setup,33,34,35 &&
./t7900-maintenance.sh --quiet --run=setup,36,40 &&
./t7900-maintenance.sh --quiet --run=setup,36,40 &&
./t7900-maintenance.sh --quiet --run=setup,36,37 &&
./t7900-maintenance.sh --quiet --run=setup,15,23,24 &&
printf "\nAll passed\n" ||
printf '\n***Failed***\n'
```

§ CI

The CI failed but it didn't look relevant.

https://github.com/LemmingAvalanche/git/actions/runs/6518415327/job/17703822606

Cheers

Kristoffer Haugsbakk (8):
t7900: remove register dependency
t7900: setup and tear down clones
t7900: create commit so that branch is born
t7900: factor out inheritance test dependency
t7900: factor out common schedule setup
t7900: fix pfx dependency
t7900: fix print-args dependency
t7900: factor out packfile dependency

 t/t7900-maintenance.sh | 49 ++++++++++++++++++++++++++++++++++++------
 1 file changed, 43 insertions(+), 6 deletions(-)

base-commit: 43c8a30d150ecede9709c1f2527c8fba92c65f40 --
2.42.0.2.g879ad04204