weval: update wizer dep, and include miscellaneous debugging helpers.

This updates weval as part of an effort to update to the latest
SpiderMonkey in wevaled-SpiderMonkey builds and latest wasi-sdk. In
particular:

- Updates to Wizer 9.0, which supports reftypes natively (emitted by
  the latest LLVM in recent wasi-sdk).
- Adds more detailed log messages in certain cases, helpful for
  tracking down reasons for non-specialized code due to changes in
  code structure or LLVM optimizations.
- Adds an intrinsic (`assert_specialized`) that I found useful during
  said debugging.

Author: cfallin