Remove merging capability from forms

[CarolineDenis]

Fixes #3836

[melton-jason]

Not a huge fan of simply removing something because of an issue.
Finding a solution would be infinitely better.

However, this is not a major component of record merging, and there is considerable pressure to get the release out, which is why this is a barely acceptable change.

If we do remove a feature from the code, it should be easy to identify what the previous implementation was, and/or why it was removed.

[maxpatiiuk]

Just like Jason said, I don't like this solution, but for not delaying the release let's have it.

For a proper fix, you can just tell the Search Dialog to exclude the current record using an extra Filter:

specify7/specifyweb/frontend/js_src/lib/components/SearchDialog/index.tsx

Line 56 in 207df9a

readonly extraFilters: RA<QueryComboBoxFilter<SCHEMA>> | undefined;

---

edit: looks like that is already done

specify7/specifyweb/frontend/js_src/lib/components/FormMeta/MergeRecord.tsx

Lines 61 to 66 in 207df9a

	{
	field: 'id',
	operation: 'in',
	isNot: true,
	value: resource.id.toString(),
	},

the reason it doesn't work is that those extra filters were only respected by regular search, not query builder search until xml-editor branch (this branch likely doesn't have the fix)

thus the issue would likely fix itself in 7.10

if not, just call deduplicate selected resources once selected and abort if there is only one

[realVinayak]

The actual fix would be on the backend - it is integrity error if trying to merge into self.

That is, the backend should bail out in that case. It shouldn't be just the frontend catch for this.