patch 8.2.1762: when a timer uses :stopinsert completion isn't stopped

Problem:    When a timer uses :stopinsert Insert mode completion isn't
            stopped. (Stanley Chan)
Solution:   Call ins_compl_prep(ESC).

src/edit.c

@@ -587,8 +587,11 @@ edit(
 		if (stop_insert_mode)
 		{
 		    // Insert mode ended, possibly from a callback.
+		    if (c != K_IGNORE && c != K_NOP)
+			vungetc(c);
 		    count = 0;
 		    nomove = TRUE;
+		    ins_compl_prep(ESC);
 		    goto doESCkey;
 		}
 	    } while (c == K_IGNORE || c == K_NOP);

src/testdir/dumps/Test_pum_stopped_by_timer.dump

@@ -0,0 +1,12 @@
+|h+0&#ffffff0|e|l@1|o| @69
+|h|u|l@1|o| @69
+|h|e@2>e| @69
+|h|e|l@1|o| @69
+|~+0#4040ff13&| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+| +0#0000000&@56|3|,|5| @10|A|l@1| 

src/testdir/test_ins_complete.vim

@@ -407,6 +407,28 @@ func Test_ins_completeslash()
   set completeslash=
 endfunc
 
+func Test_pum_stopped_by_timer()
+  CheckScreendump
+
+  let lines =<< trim END
+    call setline(1, ['hello', 'hullo', 'heeee', ''])
+    func StartCompl()
+      call timer_start(100, { -> execute('stopinsert') })
+      call feedkeys("Gah\<C-N>")
+    endfunc
+  END
+
+  call writefile(lines, 'Xpumscript')
+  let buf = RunVimInTerminal('-S Xpumscript', #{rows: 12})
+  call term_sendkeys(buf, ":call StartCompl()\<CR>")
+  call TermWait(buf, 200)
+  call term_sendkeys(buf, "k")
+  call VerifyScreenDump(buf, 'Test_pum_stopped_by_timer', {})
+
+  call StopVimInTerminal(buf)
+  call delete('Xpumscript')
+endfunc
+
 func Test_pum_with_folds_two_tabs()
   CheckScreendump
 

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1762,
 /**/
     1761,
 /**/