Add type annotations to moving_camera.py

[henrikmidtiby]

Overview: What does this pull request change?

This PR adds type annotations to moving_camera.py.

The process of adding type annotations have led to the following changes in the code:

• moved setters closer to the associated properties (for frame_height, frame_width and frame_center)
• extracted the method _get_bounding_box

Reviewer Checklist

• The PR title is descriptive enough for the changelog, and the PR is labeled correctly
• If applicable: newly added non-private functions and classes have a docstring including a short summary and a PARAMETERS section
• If applicable: newly added functions and classes are tested

[chopan050]

LGTM!