Let's make this behave more like all the rest of the meson stuff.
This also is the first step to making it a bit more flexible so we
can define integration tests in different ways as will be seen in
the next commits.
The test was originally introduced for Ubuntu CI, as it uses
PREFER_NSPAWN=1, but it was subsequently disabled two years ago [0], so
it was pretty much useless. Let's merge it into TEST-02 and tweak it a
bit to run only certain tests under QEMU when $TEST_PREFER_NSPAWN is
set.
[0] b152adbfa9
The kernel command line may contain newlines which kernel happily
accepts, but we'd ignore everything past the first newline. Let's fix
that by replacing read_one_line_file() with read_full_file().
Since c6552ad we now try to collect coverage even in situations where
it's basically impossible (like in test-mount-util where the whole / is
mounted as read-only). As dealing with this is not worth the trouble,
let's ignore the missing coverage errors thrown by gcov in such cases.
Specifying the test number manually is tedious and prone to errors (as
recently proven). Since we have all the necessary data to work out the
test number, let's do it automagically.
The logic to query test state was rather complex. I don't quite grok the point
of ret=$((ret+1))… But afaics, the precise result was always ignored by the
caller anyway.
When tests are executed serially (the default), it seems better to launch
the fairly generic test that runs the unittests early in the sequence.
Right now the tests are ordered based on when they were written, but
this doesn't make much sense.
