Support exporting selected resources without dependencies

[kaluluosi]

This PR is about this proposal:
Add an export option to explicitly include selected resources without dependencies #5992

• Add an export option to explicitly include selected resources without dependencies godot-proposals#5992 (comment)

[Calinou]

Tested locally (rebased on top of master 67c96c8), it works as expected.

Testing project: truck_town_dlc.zip

Place either of these files as dlc.zip in the same folder as the exported executable (or editor executable):

• dlc_with_dependencies.zip
• dlc_no_dependencies.zip

Both have the same effect (turning the grass blue), but dlc_no_dependencies.zip is much smaller as it doesn't include the texture files, just the changed material file.

Some feedback:

The list of export mode options should be reordered, as the Export as dedicated server option should always be last:

I would list the new option below Export selected resources (and dependencies), but above Export selected resources in the project except resources checked below.

[NetCodersX]

Will it be released together with 4.5 dev 4?