vim-patch:9.1.1203: matchparen keeps cursor on case label in sh filetype (#32900)

Problem:  matchparen keeps cursor on case label in sh filetype
          (@categorical, after 9.1.1187).
Solution: Use :defer so that cursor is always restored, remove checks
          for older Vims, finish early if Vim does not support :defer

fixes: vim/vim#16887
closes: vim/vim#16888

47071c6076

test/functional/legacy/matchparen_spec.lua

@@ -4,6 +4,7 @@ local Screen = require('test.functional.ui.screen')
 local clear = n.clear
 local exec = n.exec
 local feed = n.feed
+local poke_eventloop = n.poke_eventloop
 
 describe('matchparen', function()
   before_each(clear)
@@ -238,5 +239,26 @@ describe('matchparen', function()
       {1:~                                       }|*2
                                               |
     ]])
+    -- Send keys one by one so that CursorMoved is triggered.
+    for _, c in ipairs({ 'A', ' ', 'f', 'o', 'o', 'b', 'a', 'r' }) do
+      feed(c)
+      poke_eventloop()
+    end
+    screen:expect([[
+      {18:#!/bin/sh}                               |
+      {25:SUSUWU_PRINT() (}                        |
+        {15:case} {15:"}{100:${LEVEL}}{15:"} {15:in}                    |
+          {15:"}{100:$SUSUWU_SH_NOTICE}{15:")} foobar^         |
+          {100:${SUSUWU_S}} {15:&&} {15:return} {26:1}             |
+        {15:;;}                                    |
+          {15:"}{100:$SUSUWU_SH_DEBUG}{15:")}                 |
+          {100:(}{15:!} {100:${SUSUWU_VERBOSE})} {15:&&} {15:return} {26:1}   |
+        {15:;;}                                    |
+        {15:esac}                                  |
+        {18:# snip}                                |
+      {25:)}                                       |
+      {1:~                                       }|*2
+      {5:-- INSERT --}                            |
+    ]])
   end)
 end)