Bug
1805626 - Query vert attrib buffer binding directly. r=gfx-reviewers,lsalzman
Previously we were querying the current ARRAY_BUFFER_BINDING, which
would fail if you did:
```
BindBuffer(ARRAY_BUFFER, a)
VertexAttribPointer(...)
BindBuffer(ARRAY_BUFFER, b)
```
We would assume we should call VeretxAttribPointer again with `b` bound,
when we need to bind `a` instead.
Unfortunately, this is hard to test, and we only hit this on drivers
where we don't use VAOs, which are rare now.
Differential Revision: https://phabricator.services.mozilla.com/
D164744