obs-scripting: Add missing calldata types

[Penwy]

Description

This adds to the obspython and obslua APIs the functions calldata_scene, calldata_output and calldata_canvas, allowing retrieving said data types from a calldata object.

Motivation and Context

Being able to use signals, in particular the scene and output ones is direly needed.

How Has This Been Tested?

Ran scripts to verify the functions worked properly, returned usable object and did not crash.

Types of changes

• New feature (non-breaking change which adds functionality)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.