test: split into shorter subtests

test: split into shorter subtests

Based on Michael initial idea of separating the file-prefix subtest in
the eal flags test.

Let's split the biggest tests into their subparts.
It is then easier to have them fit in the 10s timeout we have configured
in Travis.
We also get a better idea of which part fails in the previously big tests
we had.

Those new subtests are called from the meson testsuite.
The autotest tool is left untouched.

Note: we still have an issue with test_hash_readwrite_lf.c, any help from
the original authors would be appreciated.

Signed-off-by: David Marchand <david.marchand@redhat.com>