EDSC: support 'for' loops with dynamic bounds

The existing implementation in EDSC of 'for' loops in MLIREmitter is
unnecessarily restricted to constant bounds.  The underlying AffineForOp can be
constructed from (a list of) Values and AffineMaps instead of constants.  Its
verifier will check that the "affine provenance" conditions, i.e. that the
values used in the loop conditions are defined in such a way that they can be
analyzed by affine passes, are respected.  One can use non-constant values in
affine loop bounds in conjunction with a single-dimensional identity affine
map.  Implement this in MLIREmitter while maintaining the special case for
constant bounds that leads to significantly simpler generated IR when
applicable.

Test this change using the EDSC lowering test pass to inject code emitted from
EDSC into functions with predefined names.

PiperOrigin-RevId: 233578220