feat: finish high-level Solidity parser

[DaniPopes]

Motivation

Finish parser

Solution

Parse (but not expand in sol!):

• enums
• constructor, fallback, receive, modifiers as functions
• pragmas
• imports
• using
• remaining types
  • functions
  • mappings

Add tests for flattened sources. Some of these need patches because they have to be valid Rust tokens, which means:

• no single quote strings
• no unknown string prefixes (hex, unicode)
• no invalid escapes (Solidity \uXXXX vs Rust \u{XXXX})
• (i assume) no invalid nested block comments (/* ... /*/ <-- parses the last 3 chars /*/ as the start of a nested block comment instead of the end of the first one)

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes