Support for Boolean Operations and Relations

This MR adds support for boolean operations and relations to the backend.

• AST Nodes: Introduce AST nodes for boolean operators and relations
• Freeze: Add freeze support for sp.Rels and sp.logic.boolalg.BooleanFunctions
• Typifier: Add typifier support for relations and booleans
• Printing: Add printing support for boolean operators and relations
• Constant Folding: Extend EliminateConstants to fold booleans and relations
• Branch Elimination: Add a pass to eliminate branches

Condition analysis w.r.t loop counters is reserved for future work.

Changes on the side:

• Add traits PsNumericOpTrait, PsIntOpTrait and PsBoolOpTrait to simplify typification of unary and binary operators
• Fix behaviour of EliminateConstants on unary negation
• Refactor the printer's precedence table to exactly reflect cppreference.com