patch 9.1.0124: display of below/right virtual text with non-virtual text overlap

Problem:  Virtual text with text_align 'right'/'below' wasn't being
          used when a non-virtual text property overlaps with the end of
          the line. This was because the non-virtual text property had a
          higher priority, preventing the virtual text from being used.
Solution: Fix the sorting of text properties so virtual text properties
          have a higher priority than non-virtual text properties.
          (Dylan Thacker-Smith)

related: #14063

Signed-off-by: Dylan Thacker-Smith <dylan.ah.smith@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_textprop.vim b/src/testdir/test_textprop.vim
index 97fea60..18ff3df 100644
--- a/src/testdir/test_textprop.vim
+++ b/src/testdir/test_textprop.vim
@@ -4090,6 +4090,46 @@
   call StopVimInTerminal(buf)
 endfunc
 
+func Test_virtual_text_overlap_with_highlight()
+  CheckRunVimInTerminal
+
+  let lines =<< trim END
+      vim9script
+      setline(1, ['one', 'two', 'three', 'four', 'five'])
+      set number
+
+      prop_type_add('demo_highlight_warning', {highlight: 'WarningMsg'})
+      prop_type_add('demo_virtual_text_error', {highlight: 'Error'})
+
+      prop_add(2, 4, {
+        type: 'demo_highlight_warning',
+        end_col: 4,
+      })
+      prop_add(2, 0, {
+        type: 'demo_virtual_text_error',
+        text: 'syntax error',
+        text_align: 'below',
+      })
+      normal 2j
+
+      prop_add(4, 4, {
+        type: 'demo_highlight_warning',
+        end_lnum: 5,
+        end_col: 1,
+      })
+      prop_add(4, 0, {
+        type: 'demo_virtual_text_error',
+        text: 'other error',
+        text_align: 'right',
+      })
+  END
+  call writefile(lines, 'XVirtualTextOverlapWithHighlight', 'D')
+  let buf = RunVimInTerminal('-S XVirtualTextOverlapWithHighlight', #{rows: 8, cols: 60})
+  call VerifyScreenDump(buf, 'Test_virtual_text_overlap_with_highlight_1', {})
+
+  call StopVimInTerminal(buf)
+endfunc
+
 func Test_virtual_text_in_popup_highlight()
   CheckRunVimInTerminal