Add support for EEP 79 native records syntax

[sile]

This PR implements parser and formatter support for Erlang EEP 79 native records, which introduces an alternative record syntax with module qualification and anonymous record operations.

Key Changes

Record Expressions (expressions/records.rs):

• Introduce RecordName struct to accept atoms, keywords, or variables as record names (excluding underscore)
• Introduce QualifiedRecordName struct to support module-qualified names like #mod:state{}
• Introduce RecordNameRef enum to handle both named and anonymous (#_{}) record references
• Update RecordConstructExpr, RecordIndexExpr, and RecordUpdateExpr to use the new name types
• Add comprehensive test cases for qualified and anonymous record syntax

Record Declarations (forms.rs):

• Split RecordDecl into two variants: TupleRecordDecl (traditional syntax) and NativeRecordDecl (new syntax)
• Introduce NativeRecordName struct (similar to expression names)
• Implement native record declarations with syntax: -record #Name(TVar1, ...) { fields }.
• Support optional type parameters for native records
• Add accessor methods: is_native() and type_params()
• Add test cases for native record declarations including keywords and variables as names

Import Changes:

• Remove unused Either import from expressions.rs
• Add ColonSymbol and SharpSymbol imports to forms.rs
• Add KeywordToken imports where needed

This implementation aligns with EEP 79 specification while maintaining backward compatibility with existing tuple-based record syntax.