patch 9.1.1370: CI Tests favor GTK2 over GTK3

Problem:  CI Tests favor GTK2 over GTK3
Solution: Install GTK3 dependencies and debug packages for CI workflows,
          update ASAN suppression list, update required dependency
          checks for the tests (Drew Vogel)

closes: #17253

Signed-off-by: Drew Vogel <dvogel@github>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_diffmode.vim b/src/testdir/test_diffmode.vim
index d0c2f18..dadffec 100644
--- a/src/testdir/test_diffmode.vim
+++ b/src/testdir/test_diffmode.vim
Binary files differ