EDSC: emit composed affine maps again

The recent rework of MLIREmitter switched to using the generic call to
`builder.createOperation` from OperationState instead of individual customized
calls to `builder.create<>`.  As a result, regular non-composed affine apply
operations where emitted.  Introduce a special case in Expr::build to always
create composed affine maps instead, as it used to be the case before the
rework.

Such special-casing goes against the idea of EDSC generality and extensibility.
Instead, we should consider declaring the composed form canonical for
affine.apply operations and using the builder support for creating operations
and canonicalizing them immediately (ongoing effort).

PiperOrigin-RevId: 234790129