Add "Default Project Path" to Project Manager's Quick Settings

[Meorge]

Closes godotengine/godot-proposals#11224.

This PR adds "Default Project Path" to the Project Manager's Quick Settings menu. Since this setting will mostly (exclusively?) be used from the Project Manager, and before a project in a location is created, this seems like a more natural place for it. (Of course, it is still accessible from the Editor Settings within the Editor.)

Godot.Default.Project.Path.in.Project.Manager.mp4

[Calinou]

Tested locally, it works as expected.

On the other hand, I'd prefer a solution like godotengine/godot-proposals#1312 which is more intuitive as users will discover it automatically. It would probably require less code to be implemented too.

PS: While testing this PR, I found a bug that also happens in 4.3.stable: #99689

[Meorge]

Thanks for testing it! 😄

That is a good point you bring up about it just defaulting to the path that the last project was saved in. With this PR, even though the setting is accessible from the Project Manager, it's still fairly out of the way, and a newcomer may not think to check the "Settings" page to configure their project path before going in to create a new project. Most programs do keep track of the last save location, and default to that, so the behavior from that proposal would also align more with a standard.

One sort-of-downside I see to that proposed alternate solution is that it might make the "Default Project Path" property as a whole kind of useless as a configurable editor property, since it would effectively just apply to the single next project you create (i.e., if you create another project in a different directory, it'd overwrite the property value to that). So if we were to go that route, it wouldn't make sense to me for it to be exposed as a property in either the editor or the Project Manager settings.