Add op create helper on CFG and ML builder.

Add create function on builder to make it easier to create ops of registered types. Enables doing `builder.create<AddFOp>(lhs, rhs)` as well as having default values on the build method.

This CL does not add a default build method (i.e., create<DimOp>(...) would fail).

PiperOrigin-RevId: 207268882