[EPIC] Display & Persist customisations when upgrading roads and rails

[Sipke82]

EPIC:

• Parking restrictions
• Vehicle type restrictions
• Lane arrows -- this one is covered in When a junction changes, try and preserve custom Lane Arrows #457
• Lane connectors
• Junction restrictions
• Priority & Yield signs

And then

• Did you not forget to do the same for rail?

Original request from Spike82: When parking is restricted on a road. Please keep this restriction when upgrading road.

Existing Behaviour

Bulldozing or upgrading a road segment on a junction resets the customizations on it.

Desired Behaviour

Bulldozing or upgrading a road segment on a junction only resets the customizations which can not exist anymore (like arrows cannot turn to a segment which has been bulldozed), while preserving the remaining ones. An overlay animation or floating vanishing text can be used to tell the user that something is going to be removed.

[originalfoo]

This applies to other road customisations and also any affected junction customisations.

See: VictorPhilipp/Cities-Skylines-Traffic-Manager-President-Edition#122

IMO change issue title to "Persist road & junction customisations during road upgrade"

In addition, I'd add that during road upgrade it would be useful of overlays could be shown for segment that's about to be upgraded (and also any nodes that upgrade will affect).