Add support for parsing/printing the trailing type of a dialect attribute.

This cl standardizes the printing of the type of dialect attributes to work the same as other attribute kinds. The type of dialect attributes will trail the dialect specific portion:

`#` dialect-namespace `<` attr-data `>` `:` type

The attribute parsing hooks on Dialect have been updated to take an optionally null expected type for the attribute. This matches the respective parseAttribute hooks in the OpAsmParser.

PiperOrigin-RevId: 258661298