[Discussion] Remove use of `dialect_of` macro

What was the purpose of the current `Dialect`?
The `dialect_of` macro makes it difficult to modify your code whenever you add support for Dialect.
And besides the identifier support of Dialect, it seems that it can also support query (Expr).

But... if you have other intentions for macros
Since there is a problem, I would like to discuss it with the maintainers.

Read the current `Dialect` definition and `dialect_of` macro implementation, focusing on the identifier and `Expr` support mentioned in the discussion. Review the maintainers' comments to determine the intended role of the macro. Done requires an agreed design and scope, which are not established in the issue.

Written by the indexing model from the issue text.