[patch] default filename when saving layer

[kolesar]

Use case: create a new data layer, rename it and save as a file. Current JOSM pops up save as dialog with empty filename. Patched version fills default filename with name of the layer if user has renamed that. If layer was not renamed and does not have an associated file (= is called Data layer n) then filename is empty. If layer has associated filename then it is displayed.

Requires patch #12391 that keeps track if layer was renamed by the user.

Refactored telescopic contructors in FileChooserManager to builder pattern to be able to add new settings.