refactor: mp4 module

[ptpt]

This pull request focuses on refactoring the import paths and simplifying the code in multiple files within the mapillary_tools module. The main changes involve moving the simple_mp4_parser and mp4_sample_parser to a new mp4 directory, updating the import paths accordingly, and refactoring methods to improve readability and maintainability.

Refactoring and Import Path Updates:

• mapillary_tools/geotag/blackvue_parser.py: Updated import paths to use the new mp4 module and refactored the usage of simple_mp4_parser to sparser. [1] [2] [3]
• mapillary_tools/geotag/camm_builder.py: Moved construct_mp4_parser and mp4_sample_parser imports to the mp4 module.
• mapillary_tools/geotag/camm_parser.py: Updated import paths and refactored methods to use the new sparser and sample_parser from the mp4 module. [1] [2] [3] [4] [5] [6] [7] [8]
• mapillary_tools/geotag/geotag_videos_from_video.py: Updated import paths to use the new sparser from the mp4 module. [1] [2] [3] [4]
• mapillary_tools/geotag/gpmf_parser.py: Removed the simple_mp4_parser import and updated methods to use the new sample_parser from the mp4 module. [1] [2] [3] [4] [5] [6] [7]

Code Simplification:

• mapillary_tools/geotag/simple_mp4_builder.py: Updated variable naming conventions and added comments to improve code readability. [1] [2] [3]

These changes aim to make the codebase more modular and easier to maintain by organizing related functionalities into a dedicated mp4 module and improving the clarity of the code with better naming conventions and comments.