load Xenoblade X maps from casmhd and casmda files

[ScanMountGoat]

See previous merged pull requests for the steps required to add support for a new file format. This can use the existing modern DMSM format as well as https://github.com/PredatorCZ/XenoLib/blob/master/include/xenolib/msmd.hpp as a reference. Only data relevant to models needs to be loaded, so it's ok if most of the fields are unk fields. Reply to this issue with any questions if you plan on working on this.

• add support to xc3_lib for parsing the MSMD from the casmhd file
• add a file to xc3_lib for parsing the camsda streaming data structures in map/legacy.rs