anv/allocator: Drop the block_size field from block_pool

anv/allocator: Drop the block_size field from block_pool

Since the state_stream is now pulling from a state_pool, the only thing
pulling directly off the block pool is the state pool so we can just
move the block_size there.  The one exception is when we allocate
binding tables but we can just reference the state pool there as well.

The only functional change here is that we no longer grow the block pool
immediately upon creation so no BO gets allocated until our first state
allocation.

Reviewed-by: Juan A. Suarez Romero <jasuarez@igalia.com>