Add question argument to decision

What does this MR do and why?

Add question argument to decision create and update mutations

The open question a decision resolves was exposed as title, which does not describe it. question takes over that role, and title stays for now so the frontend can switch before it is removed. The two are mutually exclusive, and question maps to the title column through an alias.

Related to #632242 (closed)

Note: as this touches on decision log code that other in-flight MRs may potentially affect, some conflicts may occur if those MRs are merged first.

MR acceptance checklist

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Related to #632242 (closed)