i965: Implement ABO surface state emission.

i965: Implement ABO surface state emission.

The maximum number of atomic buffer objects is somewhat arbitrary, we
can change it in the future easily if it turns out it's not enough...

v2: Add comments with the relevant mesa dirty bits.  Fix usage of
    BRW_NEW_UNIFORM_BUFFER in the GS ABO state atom.
v3: Update binding table layout diagrams.
v4: Resolve conflicts with the recent dynamic surface index assignment changes.

Reviewed-by: Paul Berry <stereotype441@gmail.com>