draw_vertex_texture primitives have confusing UV behaviour compared to vertex buffers

[JordOfTheFlies]

Description

Simply put, vertex primitives (i.e. draw_vertex_texture) seem to automatically normalise texture coordinates to the specific texture given instead of the whole texture page (where UV [1,1] is the bottom right corner of the texture rather than the texture page), whereas vertex_buffers operate on the whole texture page.
The former resulting in wrong results when using functions like texture_get_uvs and texture_get_texel_width (the former of which is specifically stated in the manual as being of use for 2D primitive functions).
Perhaps more of an oddity if you just want to draw the entirety of a texture, but if you're trying to draw a section of a texture a whole other approach needs to be taken to get the correct UVs.

The behaviour should either consistent between functions, or the manual is changed to reflect that UVs won't work as expected with such functions and that coordinates will need to be calculated differently. The manual currently, outside of perhaps the argument names, doesn't indicate that there's any difference in how UVs work between the two functions.

Steps To Reproduce

1. Attempt to draw a sprite using any of the named function
2. The result will be wrong unless the texture page is otherwise empty

4cfeff9c-9e3b-4650-9e1e-6a1d6db54f52

[YYBartT]

Added the info, together with a general overview on using primitives and vertex buffers to the Primitives and Vertex Formats page.