fix/schema: fix string literals

schema/azschema.bnf

@@ -1,6 +1,5 @@
-_raw_string: '`' {.} '`';
-_interpreted_string: '"' {.} '"';
-string: _raw_string | _interpreted_string;
+raw_string: '`' {.} '`';
+interpreted_string: '"' {_byte_value | _little_u_value | _big_u_value | _escaped_char | ' ' - '!' | '#' - '[' | ']' - '\U0010FFFF'} '"';
 
 _unicode_value: . | _little_u_value | _big_u_value | _escaped_char;
 _byte_value: _octal_byte_value | _hex_byte_value;
@@ -60,7 +59,8 @@ ValList
     | ValList Val <<ast.AppendVal($0, $1)>>
     ;
 Val
-    : string <<ast.NewStringVal($T0)>>
+    : raw_string <<ast.NewStringVal($T0)>>
+    | interpreted_string <<ast.NewIStringVal($T0)>>
     | rune <<ast.NewRuneVal($T0)>>
     | int <<ast.NewIntVal($T0)>>
     | float <<ast.NewFloatVal($T0)>>