patch 8.1.1905: cannot set all properties of the info popup

Problem:    Cannot set all properties of the info popup.
Solution:   Add popup_findinfo().  Rename popup_getpreview() to
            popup_findpreview().
diff --git a/src/testdir/dumps/Test_popupwin_infopopup_align_3.dump b/src/testdir/dumps/Test_popupwin_infopopup_align_3.dump
index 6effda0..2599094 100644
--- a/src/testdir/dumps/Test_popupwin_infopopup_align_3.dump
+++ b/src/testdir/dumps/Test_popupwin_infopopup_align_3.dump
@@ -8,7 +8,7 @@
 |x| @7| +0#0000001#e0e0e08|w|r|d| @4|W| |e|x|t|r|a| |t|e|x|t| | +0#0000000#ffffff0@43
 |x| @7| +0#0000001#ffd7ff255|a|n|o|t|w|r|d| |W| |e|x|t|r|a| |t|e|x|t| | +0#0000000#ffffff0@43
 |x| @7| +0#0000001#ffd7ff255|n|o|a|w|r|d| @1|W| |e|x|t|r|a| |t|e|x|t| | +0#0000000#ffffff0@43
-|x| @7| +0#0000001#ffd7ff255|t|h|a|t|w|r|d| |W| |e|x|t|r|a| |t|e|x|t| | +0&#e0e0e08|w|o|r|d|s| |a|r|e| |c|o@1|l| | +0#0000000#ffffff0@27
+|x| @7| +0#0000001#ffd7ff255|t|h|a|t|w|r|d| |W| |e|x|t|r|a| |t|e|x|t| | +0#0000000#ffff4012|w|o|r|d|s| |a|r|e| |c|o@1|l| | +0&#ffffff0@27
 |t|e|s|t| |t|e|x|t| |a|w|o|r|d> @59
 |~+0#4040ff13&| @73
 |-+2#0000000&@1| |U|s|e|r| |d|e|f|i|n|e|d| |c|o|m|p|l|e|t|i|o|n| |(|^|U|^|N|^|P|)| |m+0#00e0003&|a|t|c|h| |1| |o|f| |4| +0#0000000&@26
diff --git a/src/testdir/test_popupwin.vim b/src/testdir/test_popupwin.vim
index 1f1f731..6c1ac52 100644
--- a/src/testdir/test_popupwin.vim
+++ b/src/testdir/test_popupwin.vim
@@ -2162,7 +2162,7 @@
   call term_sendkeys(buf, "/another\<CR>\<C-W>}")
   call VerifyScreenDump(buf, 'Test_popupwin_previewpopup_2', {})
 
-  call term_sendkeys(buf, ":call popup_move(popup_getpreview(), #{col: 15})\<CR>")
+  call term_sendkeys(buf, ":call popup_move(popup_findpreview(), #{col: 15})\<CR>")
   call term_sendkeys(buf, ":\<CR>")
   call VerifyScreenDump(buf, 'Test_popupwin_previewpopup_3', {})
 
@@ -2245,6 +2245,10 @@
 	      \ }
       endfunc
       call setline(1, 'text text text text text text text ')
+      func ChangeColor()
+	let id = popup_findinfo()
+	call popup_setoptions(id, #{highlight: 'InfoPopup'})
+      endfunc
   END
   return lines
 endfunc
@@ -2313,6 +2317,7 @@
   call VerifyScreenDump(buf, 'Test_popupwin_infopopup_align_2', {})
 
   call term_sendkeys(buf, "\<Esc>")
+  call term_sendkeys(buf, ":call ChangeColor()\<CR>")
   call term_sendkeys(buf, ":call setline(2, ['x']->repeat(10))\<CR>")
   call term_sendkeys(buf, "Gotest text test text\<C-X>\<C-U>")
   call VerifyScreenDump(buf, 'Test_popupwin_infopopup_align_3', {})