Use ProjectSettings path functions instead of hard-coded folder names in tests

[aaronfranke]

I was grepping through the codebase to find the helper function that returns res://.godot/editor was, and didn't find these parts of the codebase when I searched for ".godot" since the actual constant is "godot". Once I found it, I thought it would be nice to have comments here, so that people can grep for these strings to find it. Then, I realized that my search for ".godot" led me to two places in the tests where this is hard-coded, so I replaced those.

While making this PR, I also noticed that DirAccess::make_dir_recursive doesn't properly handle res:// paths, so I have to call ProjectSettings::globalize_path first, but I wonder if that's a bug and DirAccess should be fixed?

[Calinou]

While making this PR, I also noticed that DirAccess::make_dir_recursive() doesn't properly handle res:// paths, so I have to call ProjectSettings::globalize_path() first, but I wonder if that's a bug and DirAccess should be fixed?

I'm not 100% sure. It's a bit like using OS.shell_open() on res:// or user:// paths, where you also have to use ProjectSettings::globalize_path() first. (You could technically be trying to open a protocol named res:// or user://, it's just pretty unlikely.)