Unglue should be smarter when deciding which way is to change

[GerdP]

This is a follow up for #5452 and #18670
If user selects a node which connects two or more ways and presses G to unglue there will be one way which is not changed.
The current code prefers to change a way which ends at the selected node. If more ways end at the node it is a bit difficult to pretend what happens.
I see more possible criteria:

• prefer not to change an old way if it wasn't already modified
• prefer not to change the way which is member in more relations

[GerdP]

In 16300/josm:

fix #18670, #19042: Unglue ways: False positives about affected relations

• avoid to warn about possibly broken turn restrictions when we can make sure they are not broken
• when no way is selected, try to find one that produces fewer updates

TODO: handle dataset without download areas

[Klumbumbus]

Milestone renamed