[sql, core] Adds content tags to mobgroups

[Frankie-hz]

I affirm:

• I understand that if I do not agree to the following points by completing the checkboxes my PR will be ignored.
• I understand I should leave resolving conversations to the LandSandBoat team so that reviewers won't miss what was said.
• I have read and understood the Contributing Guide and the Code of Conduct.
• I have tested my code and the things my code has changed since the last commit in the PR and will test after any later commits.

What does this pull request do?

Adds content tags to mobgroups in order to turn off certain out of era mob groups and NMs.

See: #8093 for things it can simplify.

Steps to test these changes

Run: UPDATE mob_groups SET content_tag = 'WOTG' WHERE NAME = "Orcish_Grappler";
UPDATE mob_groups SET content_tag = 'WOTG' WHERE NAME = "Orcish_Mesmerizer";
!gotoid 17350669
See only fodders in the area. This was tested with and without spawn slots

[Xaver-DaRed]

Pending PR #9111 for this to be revisisted