Move `isList`, `isTuple` and `isRecord` out of the Lexer and Parser

[ssoelvsten]

The lexer (Lexer.x) and parser (Parser.y) are both treating the isList, isTuple and isRecord as language keywords (unary operations). These should really just be just yet another function. For example, this design choice makes it impossible for the List module to reexport the isList operation even though it ought to include it.

• Add the three functions to IR.hs.
• Remove everything related to these three operations in Lexer.x, Parser.y, Basics.hs, and possibly also some other files.