This commit adds extra state to `ConversionPatternRewriterImpl` to store
all modified / newly-created operations and moved / newly-created blocks
in separate lists on a per-pattern basis.
This is in preparation of the One-Shot Dialect Conversion refactoring:
the new driver will no longer maintain a list of all IR rewrites, so
information about newly-created operations (which is needed to trigger
recursive legalization) must be retained in a different data structure.
This commit is also expected to improve the performance of the existing
driver. The previous implementation iterated over all new IR
modifications and then filtered them by type. It also required an
additional pointer indirection (through `std::unique_ptr<IRRewrite>`) to
retrieve the operation/block pointer.
9ccf613b34