Refactor Expected Types During Compilation

By adding an expected type to the compilation context, it is
now possible for type checking to occur on keyset expressions
and return statements at the moment that they are being compiled.

Previously, it was necessary to tentatively compile them and then
typecheck afterward.

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

Tests/p4rseTests/ExpressionTests/SelectExpression.swift

@@ -105,7 +105,6 @@ import TreeSitterP4
         }
       };
     """
-
   let program = try #UseOkResult(Program.Compile(simple_parser_declaration))
   let parser = try #UseOkResult(program.find_parser(withName: Identifier(name: "main_parser")))
   let runtime = try #UseOkResult(P4Runtime.ParserRuntime.create(program: program))
@@ -133,7 +132,7 @@ import TreeSitterP4
     #RequireErrorResult(
       Error(
         withMessage:
-        "Error(s) parsing select cases: {81, 12}: Keyset expression type does not match selector expression type"
+        "Error(s) parsing select cases: {81, 4}: Key expression of type Boolean is not compatible with selector type Int"
       ),
       Program.Compile(simple_parser_declaration)))
 }