vim-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 vim/vim#2126)  Merged with current code.
a45551a535

Cherry-pick Test_cwindow_highlight() from patch v8.1.2040
because it is skipped.

src/nvim/testdir/test_quickfix.vim

@@ -2692,6 +2692,28 @@ func Test_cwindow_jump()
   set efm&vim
 endfunc
 
+func Test_cwindow_highlight()
+  CheckScreendump
+
+  let lines =<< trim END
+	call setline(1, ['some', 'text', 'with', 'matches'])
+	write XCwindow
+	vimgrep e XCwindow
+	redraw
+	cwindow 4
+  END
+  call writefile(lines, 'XtestCwindow')
+  let buf = RunVimInTerminal('-S XtestCwindow', #{rows: 12})
+  call VerifyScreenDump(buf, 'Test_quickfix_cwindow_1', {})
+  call term_sendkeys(buf, ":cnext\<CR>")
+  call VerifyScreenDump(buf, 'Test_quickfix_cwindow_2', {})
+
+  " clean up
+  call StopVimInTerminal(buf)
+  call delete('XtestCwindow')
+  call delete('XCwindow')
+endfunc
+
 func XvimgrepTests(cchar)
   call s:setup_commands(a:cchar)
 

src/nvim/testdir/test_startup_utf8.vim

@@ -1,5 +1,6 @@
 " Tests for startup using utf-8.
 
+source check.vim
 source shared.vim
 source screendump.vim
 
@@ -73,7 +74,7 @@ func Test_detect_ambiwidth()
 	\ 'call test_option_not_set("ambiwidth")',
 	\ 'redraw',
 	\ ], 'Xscript')
-  let buf = RunVimInTerminal('-S Xscript', {})
+  let buf = RunVimInTerminal('-S Xscript', #{keep_t_u7: 1})
   call term_wait(buf)
   call term_sendkeys(buf, "S\<C-R>=&ambiwidth\<CR>\<Esc>")
   call WaitForAssert({-> assert_match('single', term_getline(buf, 1))})