[UR] Automatically update ur_structure_type_t

[veselypeta]

Closes #563

[kbenzie]

Why can't this be new section inside registry.yml rather than a new file?

[veselypeta]

The difficulty is that registry.yml is parsed last to ensure that all declared functions have already been parsed. ur_strcture_type_t is referenced directly and thus must be parsed first. The simplest thing was to make it a separate file and parse it first - if there are any new additions that result from parsing the remaining files we then update the file.

[kbenzie]

My concern with this is people already get confused when there are conflicts in registry.yml and adding another file that could potentially have conflicts is not a nice workflow.

Could we treat registry.yml specially instead to ensure its read when we need it?

[veselypeta]

Closing in favour of #670