[mlir] Prefix pass manager options with `mlir-`

With this change, there's going to be a clear distinction between LLVM
and MLIR pass maanger options (e.g. `-mlir-print-after-all` vs
`-print-after-all`). This change is desirable from the point of view of
projects that depend on both LLVM and MLIR, e.g. Flang.

For consistency, all pass manager options in MLIR are prefixed with
`mlir-`, even options that don't have equivalents in LLVM .

Differential Revision: https://reviews.llvm.org/D123495