Large changedfields table

[dgsiegel]

I know we talked about this already here: #13761, but I've just had another look at our changedfields table. We currently have no open drafts or changed fields in our system, still the table is about 500k rows (and a few hundred MB). I've also noticed that most rows are about a very low number of fields (having the same fieldId). Would love to have a cleanup tool for this - it feels weird to just delete those rows/truncate the table, even if @brandonkelly suggested that in the issue.

[brandonkelly]

After thinking about this some more, I realized the only time changedattributes and changedfields data is needed is for drafts, and canonical elements which have at least one draft.

So I just added a new step to garbage collection which will remove any data in those tables that isn’t needed, for Craft 4.15 and 5.7 (#16531).

[dgsiegel]

@brandonkelly this is great, thanks a bunch!