vim-patch:8.2.0382: some tests fail when run under valgrind (#21936)

Problem:    Some tests fail when run under valgrind.
Solution:   Increase timeouts.

353c351bd2

Cherry-pick Test_pum_with_preview_win() from patch 8.2.0011.

Co-authored-by: Bram Moolenaar <Bram@vim.org>

src/nvim/testdir/test_debugger.vim

@@ -36,7 +36,7 @@ endfunc
 " If the expected output argument is supplied, then check for it.
 func RunDbgCmd(buf, cmd, ...)
   call term_sendkeys(a:buf, a:cmd . "\r")
-  call term_wait(a:buf)
+  call term_wait(a:buf, 20)
 
   if a:0 != 0
     let options = #{match: 'equal'}