[mlir][scf] Fix builder of WhileOp with region builder arguments.

The overload of WhileOp::build with arguments for builder functions for
the regions of the op was broken: It did not compute correctly the types
(and locations) of the region arguments, which lead to failed assertions
when the result types were different from the operand types.
Specifically, it used the result types (and operand locations) for *both*
regions, instead of the operand types (and locations) for the 'before'
region and the result types (and loecations) for the 'after' region.

Reviewed By: Mogball, mehdi_amini

Differential Revision: https://reviews.llvm.org/D142952