First draft of safe buffer info API

[ian-h-chamberlain]

Closes #14

There are a couple pieces here:

1. Add some wrapper types around the global C3D_AttrInfo and C3D_BufferInfo
2. Allow adding arbitrary slice data to the BufferInfo, returning a lifetime-bound handle to the original slice
3. Require the VBO handle when drawing arrays (encodes the index, length, and lifetime of the vertex data).

Remaining stuff to do before merging:

• [x] Finalize names for all the new APIs and add documentation
• [x] See if there's a better pattern than static ATTR_INFO: LazyLock<RwLock<AttrInfo>> (same for BufInfo). This works, but it would be nice if we also had some way to reset it via C3D_SetBufInfo so you could swap the info in and out if you needed more than 12 buffers or 16 attribs.

[ian-h-chamberlain]

Haven't gotten much feedback so just gonna merge this, if anyone has more comments I can address them later.