Improve Parsing of P4 Parsers And Continue Runtime Implementation

1. Parsing of P4 Parsers was broken: Multiple local elements and
statements were not allowed.
2. Support more functionality on scopes.
3. Refactor variable/identifier.
4. Add more tests.

Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

Tests/p4lmTests/ParserTests.swift

@@ -22,7 +22,7 @@ import TreeSitterP4
 import Foundation
 import P4
 
-import P4Macros
+import Macros
 
 @testable import Parser