[3.x] [iOS] Swift runtime support for iOS Plugins

[naithar]

Adds a use_swift_runtime key to iOS Plugin configuration in [config] section.

This should allow to use Swift-based plugins without using custom export template or manually changing exported project. This also allows to use Swift runtime only when it's required.

Related issue https://github.com/godotengine/godot/pull/46683

[akien-mga]

This went under the radar, but might be worth rebasing and re-evaluating (for 3.6 now, but maybe also 3.5.x if relevant).

CC @bruvzg for review

[akien-mga]

@naithar Are you still around to update this?

[akien-mga]

Thanks!

[hauszp]

As this is only planned for v3.6, is there a workaround to inject the dummy.swift and bridging-header.h using EditorExportPlugin or something similar? (I still don't know how to use EditorExportPlugin properly)

Edit: Nevermind, I managed to solve this using a third-party tool (https://github.com/kronenthaler/mod-pbxproj).