Erases ex.var/ex.bind pairs into SSA before dialect conversion.

A binding ex.bind(ex.var, value) is replaced by value and both operations are removed. A bare ex.var without a consuming ex.bind is left untouched and reported as unsupported by Beaver.MLIR.Conversion.Ex.

run!/1 materializes every ex.func in a module or operation. Run it before Beaver.MLIR.Conversion.Ex.plan/1.