patch 9.0.1955: Vim9: lockvar issues with objects/classes

Problem:  Vim9: lockvar issues with objects/classes
Solution: fix `get_lhs()` object/class access and avoid `SEGV`,
          make error messages more accurate.

- `get_lval()` detects/returns object/class access
- `compile_lock_unlock()` generate code for bare static and obj_arg access
- `do_lock_var()` check lval for `ll_object`/`ll_class` and fail if so.

Details:
- Add `ll_object`/`ll_class`/`ll_oi` to `lval_T`.
- Add `lockunlock_T` to `isn_T` for `is_arg` to specify handling of `lval_root` in `get_lval()`.
- In `get_lval()`, fill in `ll_object`/`ll_class`/`ll_oi` as needed; when no `[idx] or .key`, check lval_root on the way out.
- In `do_lock_var()` check for `ll_object`/`ll_class`; also bullet proof ll_dict case
  and give `Dictionay required` if problem. (not needed to avoid lockvar crash anymore)
- In `compile_lock_unlock()` compile for the class variable and func arg cases.

closes: #13174

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Ernie Rael <errael@raelity.com>
diff --git a/src/globals.h b/src/globals.h
index 68e7ef2..9937839 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -1954,6 +1954,7 @@
 EXTERN int  input_busy INIT(= 0);   // when inside get_user_input() then > 0
 
 EXTERN typval_T	*lval_root INIT(= NULL);
+EXTERN int	lval_root_is_arg INIT(= 0);
 #endif
 
 #ifdef FEAT_BEVAL_TERM