add error states for parsing tree and AST

This adds error states for `parse::Expression`, `ast::Expression`
`ResolvedType` and `AliasedType`.

Error recovery introduced by `chumsky` parser
require some default states to recover to, which was represented before
with dummy values, like unit type for expression or alias with `error` name.
However, this kind of recovery is not desirable in case of further
analyzing of parse tree, because it would lead to unrecognazible errors
on analyzer.

Author: gerau