MLIR supports operations with resizable operand lists, but this property must
be indicated during the construction of such operations. It can be done
programmatically by calling a function on OperationState. Introduce an
ODS-internal trait `ResizableOperandList` to indicate such operations are use
it when generating the bodies of various `build` functions as well as the
`parse` function when the declarative assembly format is used.
Differential Revision: https://reviews.llvm.org/D78292