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_gui.vim b/src/testdir/test_gui.vim
index 2925934..9d31996 100644
--- a/src/testdir/test_gui.vim
+++ b/src/testdir/test_gui.vim
@@ -770,13 +770,10 @@
 endfunc
 
 func Test_scrollbars()
-  " this test sometimes fails on CI
-  let g:test_is_flaky = 1
-
   " buffer with 200 lines
-  new
   call setline(1, repeat(['one', 'two'], 100))
-  set guioptions+=rlb
+  set scrolloff=0
+  set guioptions=rlbk
 
   " scroll to move line 11 at top, moves the cursor there
   let args = #{which: 'left', value: 10, dragging: 0}
@@ -826,6 +823,7 @@
   call assert_fails("call test_gui_event('scrollbar', #{which: 'a', value: 1, dragging: 0})", 'E475:')
 
   set guioptions&
+  set scrolloff&
   set wrap&
   bwipe!
 endfunc