patch 9.1.1166: command-line auto-completion hard with wildmenu

Problem:  command-line auto-completion hard with wildmenu
Solution: implement "noselect" wildoption value (Girish Palya)

When `noselect` is present in `wildmode` and 'wildmenu' is enabled, the
completion menu appears without pre-selecting the first item.

This change makes it easier to implement command-line auto-completion,
where the menu dynamically appears as characters are typed, and `<Tab>`
can be used to manually select an item. This can be achieved by
leveraging the `CmdlineChanged` event to insert `wildchar(m)`,
triggering completion menu.

Without this change, auto-completion using the 'wildmenu' mechanism is
not feasible, as it automatically inserts the first match, preventing
dynamic selection.

The following Vimscript snippet demonstrates how to configure
auto-completion using `noselect`:

```vim
vim9script
set wim=noselect:lastused,full wop=pum wcm=<C-@> wmnu
autocmd CmdlineChanged : timer_start(0, function(CmdComplete, [getcmdline()]))

def CmdComplete(cur_cmdline: string, timer: number)
  var [cmdline, curpos] = [getcmdline(), getcmdpos()]
  if cur_cmdline ==# cmdline  # Avoid completing each character in keymaps and pasted text
    && !pumvisible() && curpos == cmdline->len() + 1

    if cmdline[curpos - 2] =~ '[\w*/:]'  # Reduce noise by completing only selected characters
      feedkeys("\<C-@>", "ti")
      set eventignore+=CmdlineChanged  # Suppress redundant completion attempts
      timer_start(0, (_) => {
        getcmdline()->substitute('\%x00$', '', '')->setcmdline()  # Remove <C-@> if no completion items exist
        set eventignore-=CmdlineChanged
      })
    endif
  endif
enddef
```

fixes: #16551
closes: #16759

Signed-off-by: Girish Palya <girishji@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/doc/options.txt

@@ -1,4 +1,4 @@
-*options.txt*	For Vim version 9.1.  Last change: 2025 Mar 01
+*options.txt*	For Vim version 9.1.  Last change: 2025 Mar 02
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -9566,7 +9566,10 @@ A jump table for the options with a short description can be found at |Q_op|.
 	"lastused"	When completing buffer names and more than one buffer
 			matches, sort buffers by time last used (other than
 			the current buffer).
-	When there is only a single match, it is fully completed in all cases.
+	"noselect"	Do not pre-select first menu item and start 'wildmenu'
+			if it is enabled.
+	When there is only a single match, it is fully completed in all cases
+	except when "noselect" is present.
 
 	Examples of useful colon-separated values:
 	"longest:full"	Like "longest", but also start 'wildmenu' if it is
@@ -9589,7 +9592,11 @@ A jump table for the options with a short description can be found at |Q_op|.
 		:set wildmode=list,full
 <	List all matches without completing, then each full match >
 		:set wildmode=longest,list
-<	Complete longest common string, then list alternatives.
+<	Complete longest common string, then list alternatives >
+		:set wildmode=noselect:full
+<	Display 'wildmenu' without completing, then each full match >
+		:set wildmode=noselect:lastused,full
+<	Same as above, but sort buffers by time last used.
 	More info here: |cmdline-completion|.
 
 						*'wildoptions'* *'wop'*

runtime/doc/version9.txt

@@ -1,4 +1,4 @@
-*version9.txt*  For Vim version 9.1.  Last change: 2025 Feb 23
+*version9.txt*  For Vim version 9.1.  Last change: 2025 Mar 02
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -41605,6 +41605,8 @@ Completion: ~
 	"preinsert"	- highlight to be inserted values
 - handle multi-line completion as expected
 - improved commandline completion for the |:hi| command
+- New option value for 'wildoptions':
+  	"noselect"	- do not auto select an entry in the wildmenu
 
 Options: ~
 - the default for 'commentstring' contains whitespace padding to have