Improve find_modules with regex functionality

[casparvl]

Expand functionality of find_modules so that it can be passed a regular expression. It can also ommit the version (i.e. anything after the last slash) from the match, if required.

If you want to define a ReFrame test to play around with the new find_modules functionality:

# eessi/tests/find_modules.py
import reframe as rfm
import reframe.utility.sanity as sn

from eessi.testsuite import hooks, utils
from eessi.testsuite.constants import *

@rfm.simple_test
class find_modules(rfm.RunOnlyRegressionTest):

    # This test can run at any scale, so parameterize over all known SCALES
    valid_prog_environs = ['default']
    valid_systems = ['*']

    # Parameterize over all modules that start with X
    module_name = parameter(utils.find_modules('^gompi\/', name_only = False))

    executable = 'hostname'

    time_limit = '5m'

    # This test should be run as part of EESSI CI
    tags = {TAGS['CI']}

Then run with e.g.

reframe -C test-suite/config/izum_vega.py -c test-suite/eessi/testsuite/tests/find_modules.py -R -t CI -l

This also makes me think: do we need unittests for the test suite? I.e. tests that test the hooks & utils? It might be difficult to make some of those, e.g. how do we convince the ReFrame runtimes available_modules to return us a predetermined set of modules? But it would be worthwhile to have, as it defines the desired behaviour. It would also be very valuable for things like: does filtering work (which tests should run on which partitions), how many MPI ranks & OpenMP threads are launched, etc.

[smoors]

tested and works fine (after removing the trailing slash with name_only=True, see comment).

[smoors]

lgtm