patch 8.2.0936: some terminals misinterpret the code for getting cursor style

Problem:    Some terminals misinterpret the code for getting cursor style.
Solution:   Send a sequence to the terminal and check the result. (IWAMOTO
            Kouichi, closes #2126)  Merged with current code.
diff --git a/src/testdir/test_startup_utf8.vim b/src/testdir/test_startup_utf8.vim
index ffbc793..1684d80 100644
--- a/src/testdir/test_startup_utf8.vim
+++ b/src/testdir/test_startup_utf8.vim
@@ -1,5 +1,6 @@
 " Tests for startup using utf-8.
 
+source check.vim
 source shared.vim
 source screendump.vim
 
@@ -71,7 +72,7 @@
 	\ 'call test_option_not_set("ambiwidth")',
 	\ 'redraw',
 	\ ], 'Xscript')
-  let buf = RunVimInTerminal('-S Xscript', {})
+  let buf = RunVimInTerminal('-S Xscript', #{keep_t_u7: 1})
   call TermWait(buf)
   call term_sendkeys(buf, "S\<C-R>=&ambiwidth\<CR>\<Esc>")
   call WaitForAssert({-> assert_match('single', term_getline(buf, 1))})