Backport various fixes from !3479 (fix linking with measure LPE, fix multiple copy-pastes, fix copy-paste clones to new document)

Backports part of Jabier Arraiza's fix from a5f8da8b

Fix #387 (closed), #1743 (closed), #3035 (closed)

/cc @jabiertxof could you review?

Update: Jabier's taken a quick look at it, but he's pretty busy too. From DMs:

I see your code seems tiny and correct,

marked this merge request as ready

changed the description

added 4 commits

• 4646158a - 1 commit from branch inkscape:1.1.x
• 2a61c85d - Fix clone size on paste
• 44e63c76 - Fix pasting not forking LPEs enough
• 6d1eecd2 - Fix adding links to Measure Segments LPE

Compare with previous version

added 7 commits

• 6d1eecd2...f0ead5f8 - 4 commits from branch inkscape:1.1.x
• 62e062e3 - Fix clone size on paste
• f5378bd6 - Fix pasting not forking LPEs enough
• 9f11975f - Fix adding links to Measure Segments LPE

Compare with previous version

merged