Instead of storing type/size/normalized/pureInteger we instead store a
pointer to the angle::Format. This makes some code logic simpler and
will let us more easily check if a vertex attribute format changes in
calls to VertexAttribPointer or VertexAttribFormat.

This CL adds extra information to angle::Format to represent the vertex
format info needed. It also caches the channel count so that it can be
queried faster.

Also renames "Int" -> "Sint" in UtilsVk for consistency.

Bug: angleproject:3256
Change-Id: I5ef9b983dad8a58c341113c802500b89ce081566
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1684293
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jonah Ryan-Davis <jonahr@google.com>