[ur] Automatically generate `ur_structure_type_t`

[kbenzie]

Following on from discussion about #546 and how to make it easier for external parties to make contributions it was noted that it should be possible to completed automate making changes to the ur_structure_type_t enumeration in a similar way that the ur_function_t enumeration is automatically generated for XPTI integration.

[veselypeta]

I've been looking into this for a bit and this actually might be quite a hard problem to solve for a couple of reasons:

• The ur_structure_type_t can only be generated after all types have been parsed - i.e. all extended structs have been identified.
• The meta data-structure is generated on-the-fly with each new type parsed and parsing of extended structs rely on ur_structure_type_t to already be parsed and available in meta

One other option which occurred to me is that we generate this similarly to how the registry is handled - by automatically updating it in it's own yaml file.

[kbenzie]

One other option which occurred to me is that we generate this similarly to how the registry is handled - by automatically updating it in it's own yaml file.

Moving this into the registry is how I envisioned this working since its already automatically generated, would be better to avoid having multiple generated yaml files since this one already confuses people enough.

[veselypeta]

Closed with #670