patch 9.0.2057: Vim9: no strict type checks for funcrefs varargs

Problem:  Vim9: no strict type checks for funcrefs varargs
Solution: Perform strict type checking when declaring funcrefs
          with vararg declaration, add tests

closes: #13397

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Ernie Rael <errael@raelity.com>
diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index 701a2f0..cbbd572 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
Binary files differ