[mlir][toy] Use `make_early_inc_range` when erasing ops during iteration (#146892)
Use `make_early_inc_range` when erasing operations from a block to make
sure that the iterator is not invalidated. The previous implementation
happened to work on a "normal" dialect conversion because some IR
modifications are delayed. It no longer works with a One-Shot Dialect
Conversion. The new One-Shot Dialect Conversion API is more similar to
the normal rewriter API.