[mlir][Transform] `apply_conversion_patterns`: Update handles (#83950)

Until now, `transform.apply_conversion_patterns` consumed the target
handle and potentially invalidated handles. This commit adds tracking
functionality similar to `transform.apply_patterns`, such that handles
are no longer invalidated, but updated based on op replacements
performed by the dialect conversion.

This new functionality is hidden behind a `preserve_handles` attribute
for now.