~~This applies on top of !672, the last three commits belong here.~~
Here we compute additional "synthetic" loops that will be used to implement non-trivial forward edges using (possibly conditional) `break` instructions.
-- v3: vkd3d-shader/ir: Sort loop intervals. vkd3d-shader/ir: Generate synthetic intervals for forward edges. vkd3d-shader/ir: Compute loop as intervals of the block order.