Make weight configurable when placed in sidebar

The following translated strings have been changed/added:

• Settings summary: "Placed in sidebar" --> "Placed in sidebar (weight: @weight)"
• Settings form sidebar_weight: "Defines the position in the sidebar where the field will be placed. Default is at the end.
  To show above the path alias use a value < @pathalias_weight and to show above author information use a value < @author_weight."

I leave it to the project maintainers to reword them. The translations need to be adapted accordingly.

Closes #3452518