Put a try-guard around this import for newer pythons

[casparvl]

I ran into issues on a system which had python 3.12, which lacks pkg_resources. Essentially, you can't import anything from the eessi namespace there

[casparvl]

I can confirm that this resolved my issue:

EESSI_TESTSUITE_URL=https://github.com/casparvl/test-suite.git EESSI_TESTSUITE_BRANCH=add_import_guard EESSI_CONFIGS_TESTSUITE_URL=https://github.com/EESSI/test-suite.git EESSI_CONFIGS_TESTSUITE_BRANCH=main EESSI_CI_SYSTEM_NAME=bsc_hca ${HOME}/EESSI_CI/CI/run_reframe.sh

Now listed all tests succesfully.