Cover gix with most features but no extras

This expands the `unit-tests` recipe in the `justfile` (which is
one of the recipes the full CI `test` job runs) to add a command
that tests `gix` with all the current default features *except* for
`extras` and its subfeatures.

This appears to have been a missing potentially valuable area in
testing.

In particular, as noted in 2400158 (#1993), the Git 2.47.* bug that
caused incorrect `find_youngest_matching_commit` baselines to be
generated had applied equally to the `regex_matches` and
`contained_string_matches` tests, but only the `regex_matches`
failure was found locally in #1622 and on CI in #1635, because no
combination of features under which `contained_string_matches` runs
was tested.

Thus, `contained_string_matches` was effectively not exercised, and
regressions that it should catch, as well as the effect of possible
changes to the test if any others are ever made, were not tested.
This resulted in the mitigations for #1622 not covering that test
either (until 2400158).

This commit chooses a combination of features that may plausibly be
in practical use and that is fairly simple to specify, to fill the
gap.

(If this turns out to slow things down too much, then it could be
narrowed to only run some tests.)

This only adds a command to the recipe. It does not remove any
commands that were already there. `gix` remains tested in all the
ways it was tested before, as well as in this one new way.

Author: EliahKagan

justfile

@@ -174,6 +174,7 @@ unit-tests:
     cargo nextest run -p gix-protocol --features blocking-client
     cargo nextest run -p gix-protocol --features async-client
     cargo nextest run -p gix --no-default-features
+    cargo nextest run -p gix --no-default-features --features basic,comfort,max-performance-safe
     cargo nextest run -p gix --no-default-features --features basic,extras,comfort,need-more-recent-msrv
     cargo nextest run -p gix --features async-network-client
     cargo nextest run -p gix --features blocking-network-client