Consolidate pages referring to "Getting Involved", "Community", and "Getting Help"

These 5 pages should be consolidated into 2 pages - one on getting help (which may or may not in turn be consolidated into the documentation), and one on the community.

• https://docs.civicrm.org/user/en/latest/the-civicrm-community/the-civicrm-community/
• https://docs.civicrm.org/dev/en/latest/basics/community/
• https://civicrm.org/get-involved
• https://civicrm.org/community
• https://civicrm.org/help