[mlir] Support dialect-wide canonicalization pattern registration

* Add `hasCanonicalizer` option to Dialect.
* Initialize canonicalizer with dialect-wide canonicalization patterns.
* Add test case to TestDialect.

Dialect-wide canonicalization patterns are useful if a canonicalization pattern does not conceptually associate with any single operation, i.e., it should not be registered as part of an operation's `getCanonicalizationPatterns` function. E.g., this is the case for canonicalization patterns that match an op interface.

Differential Revision: https://reviews.llvm.org/D103226