Refactor into four major components:
1. Common: Things shared among all other components.
2. Lang: P4-language-related components.
3. Runtime: Components required to run a P4 program.
4. Parser: Components for parsing a P4 program from source.
Other components:
1. Macros
2. Tests
3. TreeSitterExtensions: Extra tree sitter functionality
Signed-off-by: Will Hawkins <hawkinsw@obs.cr>
Will Hawkins