Add overlapped option to jobstart

When UV_OVERLAPPED_PIPE was used for the pipe passed to the child process, a
problem occurred with the standard input of the .Net Framework application
(#11809). Therefore, add the overlapped option to jobstart() and change it so
that it is set only when necessary

runtime/autoload/provider.vim

@@ -3,8 +3,11 @@
 " Start the provider and perform a 'poll' request
 "
 " Returns a valid channel on success
-function! provider#Poll(argv, orig_name, log_env) abort
+function! provider#Poll(argv, orig_name, log_env, ...) abort
   let job = {'rpc': v:true, 'stderr_buffered': v:true}
+  if a:0
+    let job = extend(job, a:1)
+  endif
   try
     let channel_id = jobstart(a:argv, job)
     if channel_id > 0 && rpcrequest(channel_id, 'poll') ==# 'ok'

runtime/autoload/provider/pythonx.vim

@@ -19,7 +19,7 @@ function! provider#pythonx#Require(host) abort
     call add(args, plugin.path)
   endfor
 
-  return provider#Poll(args, a:host.orig_name, '$NVIM_PYTHON_LOG_FILE')
+  return provider#Poll(args, a:host.orig_name, '$NVIM_PYTHON_LOG_FILE', {'overlapped': v:true})
 endfunction
 
 function! s:get_python_executable_from_host_var(major_version) abort

runtime/doc/eval.txt

@@ -5506,6 +5506,11 @@ jobstart({cmd}[, {opts}])				*jobstart()*
 			      stdout data.
 		  |on_stderr|:  (function) Callback invoked when the job emits
 			      stderr data.
+		  overlapped: (boolean) Set FILE_FLAG_OVERLAPPED for the
+			      standard input/output passed to the child process.
+			      Normally you do not need to set this.
+			      (Only available on MS-Windows, On other
+			      platforms, this option is silently ignored.)
 		  pty:	      (boolean) Connect the job to a new pseudo
 			      terminal, and its streams to the master file
 			      descriptor. Then  `on_stderr` is ignored,