[mlir] GreedyPatternRewriteDriver: Add new strict mode option

There are now three options:
* `AnyOp` (previously `false`)
* `ExistingAndNewOps` (previously `true`)
* `ExistingOps`: this one is new.

The last option corresponds to what the `applyOpPatternsAndFold(Operation*, ...)` overload is doing. It is now also supported on the `applyOpPatternsAndFold(ArrayRef<Operation *>, ...)` overload.

Differential Revision: https://reviews.llvm.org/D141904