The new flag, `--mlir-print-skip-regions`, sets the op printing option
that disables region printing. This results in the usual
`--mlir-print-ir-*` debug options printing only the names of the
executed passes and the signatures of the ops.
Example:
```mlir
// -----// IR Dump Before CSE (cse) //----- //
func.func @bar(%arg0: f32, %arg1: f32) -> f32 {...}
// -----// IR Dump Before Canonicalizer (canonicalize) //----- //
func.func @bar(%arg0: f32, %arg1: f32) -> f32 {...}
```
The main use-case is to be triage compilation issues (crashes, slowness)
on very deep pass pipelines and with very large IR files, where printing
IR is prohibitively slow otherwise.
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