[mlir][linalg] Avoid template methods for parsing and printing.

The revision avoids template methods for parsing and printing that are replicated for every named operation. Instead, the new methods take a regionBuilder argument. The revision reduces the compile time of LinalgOps.cpp from 11.2 to 10.2 seconds (debug build).

Reviewed By: nicolasvasilache

Differential Revision: https://reviews.llvm.org/D123987