Fix batch rename for unique name and empty name

[ajreckof]

Fixes #78290
Fixes #78291

[ajreckof]

Implemented what kobewi suggested with both it now look like this.

sorry I just found a rather important bug xd

[KoBeWi]

The approach for appending errors needs to be reworked, as it's possible to stack errors from multiple nodes:

[Calinou]

Tested locally (rebased on top of master cb73a6e), it works.

However, I can only confirm the first case (empty node name) is resolved, as I can't test the second issue. I never see the Batch Rename option in the context menu when selecting several nodes if both are scene-unique, and this also applies in master.

Approving nonetheless, as this is an improvement over the existing situation.

[KoBeWi]

I never see the Batch Rename option in the context menu when selecting several nodes

Batch Rename does not appear if you select a parent and child node together. Likely a bug.

[ajreckof]

I never see the Batch Rename option in the context menu when selecting several nodes

Batch Rename does not appear if you select a parent and child node together. Likely a bug.

Indeed See #76069

[YuriSizov]

Besides a review from @KoBeWi this also needs a rebase.

[ajreckof]

So I rebased this. The conflicting fix was about making sure it wouldn't raise an error when renaming a node to the same name when it is an unique name in owner. I moved this fix to the new places from this PR

[YuriSizov]

I think the added meta should be prefixed with "_" by convention. Otherwise, this seems to address @KoBeWi's concern, albeit in a rather awkward way. Can't we set the meta and then compose a line by checking for each possible key, instead of doing this nested if thing?

[KoBeWi]

Suggested change

	// we previously made sure name is not the same as current name so that it wonn't complain about already used unique name when not changing name
	// We previously made sure name is not the same as current name so that it won't complain about already used unique name when not changing name.

[akien-mga]

Poke @ajreckof, would be good to fix this before merging.

[KoBeWi]

I think the added meta should be prefixed with "_" by convention.

This convention is irrelevant for internal editor nodes.

[akien-mga]

Thanks!