Merge parse_token_trees_until_close_delim and parse_all_token_trees.

Because they're very similar, and this will allow some follow-up
changes.

compiler/rustc_parse/src/lexer/mod.rs

@@ -52,7 +52,7 @@ pub(crate) fn parse_token_trees<'a>(
     let cursor = Cursor::new(src);
     let string_reader =
         StringReader { sess, start_pos, pos: start_pos, src, cursor, override_span };
-    tokentrees::TokenTreesReader::parse_token_trees(string_reader)
+    tokentrees::TokenTreesReader::parse_all_token_trees(string_reader)
 }
 
 struct StringReader<'a> {