Implement parametric tiling on standard for loops

Parametric tiling can be used to extract outer loops with fixed number of
iterations.  This in turn enables mapping to GPU kernels on a fixed grid
independently of the range of the original loops, which may be unknown
statically, making the kernel adaptable to different sizes.  Provide a utility
function that also computes the parametric tile size given the range of the
loop.  Exercise the utility function through a simple pass that applies it to
all top-level loop nests.  Permutability or parallelism checks must be
performed before calling this utility function in actual passes.

Note that parametric tiling cannot be implemented in a purely affine way,
although it can be encoded using semi-affine maps.  The choice to implement it
on standard loops is guided by them being the common representation between
Affine loops, Linalg and GPU kernels.

PiperOrigin-RevId: 257180251