fix(shell): on Windows :make does not echo #22728

Problem:
On Windows, :make does not display the output of the program it runs.
The cause is the default 'shellpipe'.  On Linux, nvim uses `tee` to redirect the
output to both stdout and the error file.  In Windows, for both cmd.exe and
powershell, the output is only redirected to the error file.

Solution:
- On Windows, change the 'shellpipe' default to "2>&1| tee".
    - Nvim includes `tee` in its Windows package.
- Document recommended defaults for powershell.

Fixes #12910

test/functional/vimscript/system_spec.lua

@@ -644,12 +644,12 @@ describe('shell :!', function()
     if is_os('win') then
       feed(':4verbose %!sort /R<cr>')
       screen:expect{
-        any=[[Executing command: .?& { Get%-Content .* | & sort /R } 2>&1 | Out%-File %-Encoding UTF8 .*; exit $LastExitCode"]]
+        any=[[Executing command: .?& { Get%-Content .* | & sort /R } 2>&1 | %%{ "$_" } | Out%-File .*; exit $LastExitCode"]]
       }
     else
       feed(':4verbose %!sort -r<cr>')
       screen:expect{
-        any=[[Executing command: .?& { Get%-Content .* | & sort %-r } 2>&1 | Out%-File %-Encoding UTF8 .*; exit $LastExitCode"]]
+        any=[[Executing command: .?& { Get%-Content .* | & sort %-r } 2>&1 | %%{ "$_" } | Out%-File .*; exit $LastExitCode"]]
       }
     end
     feed('<CR>')