
This commit improves the `allowPatternRollback` flag handling in the dialect conversion driver. Previously, this flag was used to merely detect cases that are incompatible with the new One-Shot Dialect Conversion driver. This commit implements the driver itself: when the flag is set to "false", all IR changes are materialized immediately, bypassing the `IRRewrite` and `ConversionValueMapping` infrastructure. A few selected test cases now run with both the old and the new driver. RFC: https://discourse.llvm.org/t/rfc-a-new-one-shot-dialect-conversion-driver/79083