After the merge of conversion transactions into one under RHELC-576 we've removed the unused function 'call_yum_cmd_w_downgrades()' (https://github.com/oamg/convert2rhel/pull/669). This function was calling other functions which are now not used anywhere and can be removed.

Acceptance criteria

• The now unused functions resolve_dep_errors() and get_problematic_pkgs() are removed.
• We've made sure that all the related integration tests are removed.