Fix ProjectSettings has_setting() when used on a overriden setting with feature tags

[BimDav]

Fixed #57970

[akien-mga]

That seems consistent with the _get/get_setting implementation indeed.

[akien-mga]

Thanks!

[akien-mga]

Cherry-picked for 3.5.

[akien-mga]

Cherry-picked for 3.4.3.

[akien-mga]

As discussed in #58294, this causes issues due to the way this API is used. has_setting (and set_setting) seem to be used to match exact setting names, and they should not remap to feature overrides.

The use case in #57970 seem to actually be a more complex issue than just handling feature overrides. The code before this PR would work fine if both the base setting and its feature override were defined in the Project Settings directly. The issue here seems to come from defining the base setting in a plugin and overriding it in the project. This PR likely even breaks the use case in the MRP as it uses has_setting to reproduce GLOBAL_DEF and that likely means that the base setting will not be defined because it's matching its feature override in project.godot (which is loaded first).