Scene is marked dirty/modified when unrelated resources are modified

[Flavelius]

Godot version:

3.2.4.beta6.mono.official

OS/device including version:

Win10

Issue description:

Whenever a resource is modified while a scene is open, no matter whether the resource is used in the scene or not, the scene get's marked as modified too.

Steps to reproduce:
Create and open a scene, modify some unrelated resource, notice the asterisk appear in the scene tab.

[Calinou]

Since the editor can't be marked dirty (only scenes can), I believe this is done so that you get an "unsaved changes" warning when exiting the editor. Now that #32321 was merged, we need to be especially careful about avoiding false negatives.

[Flavelius]

If the editor has to keep track of the dirty resources it has to have knowledge of the dirty state somehow in my logic; i see no reason why it couldn't include the asterisk in the application title for it like most other software does. Maybe it's more complicated internally, but as communication to the user it would make it clearer than pretending the scene has been changed when it actually hasn't, just as a workaround. And it could still warn about unsaved changes before exiting unrelated to that.