patch 9.0.1951: Vim9: hard to debug vim9_class errors from CI

Problem:  Vim9: hard to debug vim9_class errors from CI
Solution: Include the line number in assert_xxx() calls.  Include the
          entire error message in the tests.  Fix the indentation in the
          test file.  Add tags for new error codes.

closes: #13206

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>
diff --git a/src/version.c b/src/version.c
index 0bb2239..5aca53a 100644
--- a/src/version.c
+++ b/src/version.c
@@ -700,6 +700,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1951,
+/**/
     1950,
 /**/
     1949,