Added camera feed and plane detection (both vertical and horizontal)

[elmajime]

Camera feed is functional if using branch https://github.com/elmajime/godot/tree/camera_from_external_feed for Godot. A Merge request have been created on Godot's repository. The link to the MR is available in the proposal https://github.com/godotengine/godot-proposals/issues/10678.

This adds camera feed display and plane detection.

Code is present to handle light and depth estimation too but the later needs a new feature in Godot. The light estimation doesn't work quiet yet.

Remaining will be :

• shrinking planes when needed (right now they just grow)
• correct handling of phone orientation (hard coded as being in landscape mode)
• implement depth estimation use in Godot's repository and reactivate the dedicated code in this one
• correct light estimation
• implement point cloud display
• implement image detection
• make a nicer demo