* [TIR] Remove ProducerConsumer and AllocateNode::new_expr

This PR removes two legacy IR parts in TIR that are deprecated.

ProducerConsumer node only serves as a hint markup and may no longer be
informative after extensive transformations in the pass.
If necessary, we can add related info via AttrStmt.

The new_expr field in the AllocateNode is deprecated since it can just be
replaced by a LetStmt.

- Remove dependencies of passes on ProducerConsumer.
- Remove ProducerConsumer from the IR.
- Remove the deprecated fields (new_expr, free_function) from AllocateNode.

* Fix additional testcases