[ODS] Implement a new 'hasCanonicalizeMethod' bit for cann patterns.

This provides a simplified way to implement 'matchAndRewrite' style
canonicalization patterns for ops that don't need the full power of
RewritePatterns.  Using this style, you can implement a static method
with a signature like:

```
LogicalResult AssertOp::canonicalize(AssertOp op, PatternRewriter &rewriter) {
  return success();
}
```

instead of dealing with defining RewritePattern subclasses.  This also
adopts this for a few canonicalization patterns in the std dialect to
show how it works.

Differential Revision: https://reviews.llvm.org/D99143