[test] Enhance .testcore testcases w/ db checks (preparation)

[mmd-osm]

PR with prep steps to address #487

• XML parser can now be reused in other scenarios where we don't need the staticxml_backend.
• Reusable functions in test_core are now in test_core_helper.
• Migrate test_core to Catch2

TODO for next PR:

• create another test_apidb_backend_* for testcore test cases
• initialize test data, write xml contents to db

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This PR also includes two left over unit tests for options and backend roles. Coverage for options.cpp was improved by adding missing test cases. Roles check now includes "importer" role.

sudo support was added for the devcontainer.