Add support for georeferencing vector layers in georeferencer

[nyalldawson]

Allows vector layers without spatial referencing to be interactively georeferenced (or layers with referencing to be re-referenced!).

Georeferencing occurs in a task, so it remains nice and responsive even with massive layers.

Sponsored by the Danish QGIS Usergroup

This PR builds on the work started by @roya0045 in #41386 -- full credit to Alex for the groundwork here!

Fixes #41300

[github-actions]

@nyalldawson
This pull request has been tagged as requiring documentation.

A documentation ticket will be opened at https://github.com/qgis/QGIS-Documentation when this PR is merged.

Please update the description (not the comments) with helpful description and screenshot to help the work from documentors.
Also, any commit having [needs-doc] or [Needs Documentation] in will see its message pushed to the issue, so please be as verbose as you can.

Thank you!

[nyalldawson]

@roya0045 would love some feedback if you have a chance to build and test this branch!

[nyalldawson]

@3nids all done!

[roya0045]

@roya0045 would love some feedback if you have a chance to build and test this branch!

I don't think I can provide timely feedback, the sooner I might be able to do is this weekend and that might be unrealistic. I don't doubt the quality of the changes, the only element that I had issues with my own version was the exporter. It converted any outputs to a geopackage and I couldn't figure out why this format was imposed despite calling the exporter 'properly'.

Did you manage to find out what was causing this issue with the QgsVectorFileWriter?

[nyalldawson]

@roya0045

I don't think I can provide timely feedback, the sooner I might be able to do is this weekend and that might be unrealistic. I don't doubt the quality of the changes, the only element that I had issues with my own version was the exporter. It converted any outputs to a geopackage and I couldn't figure out why this format was imposed despite calling the exporter 'properly'.

Did you manage to find out what was causing this issue with the QgsVectorFileWriter?

Ah, good catch! Fixed in b03611c.

[roya0045]

If that's fixed I assume the remainder is fine. 👍

[nirvn]

@nyalldawson , I feel like an editor who's trying to justify his salary by pointing out frivolous issues here ;) small formatting comments added, couldn't find anything fundamentally wrong.

[nyalldawson]

Thanks @nirvn, all addressed!

[github-actions]

@nyalldawson
A documentation ticket has been opened at qgis/QGIS-Documentation#7384
It is your responsibility to visit this ticket and add as much detail as possible for the documentation team to correctly document this change.
Thank you!

[agiudiceandrea]

@nyalldawson, may this PR be the cause of #51197 and #51299?

[roya0045]

@nyalldawson, may this PR be the cause of #51197 and #51299?

Would be more likely to have been caused by something during the rework ( the previous PR affecting the georeferencer I recall). Regardless, of when, there's something to fix.

[agiudiceandrea]

Would be more likely to have been caused by something during the rework

@roya0045, if you are referring to #47141 ("Fix lots of georeferencer issues") and #47279 ("Georeferencer fixes, pt 2"), they have been both allegedly backported to 3.22 (#47276), so the issues should have occurred also in version 3.22, while it seems not the case.