Propose simplifying/combining community engagement roles [MNG-2415]

Proposes:

See https://tasks.opencraft.com/browse/MNG-2415?focusedCommentId=223242&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-223242 for my explanation of the changes proposed here:

Some of these changes are temporarily put into the "Community Liaison" role, but @nizarmah is proposing to turn that into a Developer Advocate role which will come in a future PR.