gst-env: Add support for PowerShell 7

The executable binary name of "PowerShell 7" is "pwsh.exe"
which is different from system default installed
"Windows PowerShell (version 5.x or older)"

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/2545>

Author: seungha-yang

data/misc/cmd_or_ps.ps1

@@ -2,7 +2,7 @@ $i=1
 $ppid=(gwmi win32_process -Filter "processid='$pid'").parentprocessid
 $pname=(Get-Process -id $ppid).Name
 While($true) {
-  if($pname -eq "cmd" -Or $pname -eq "powershell") {
+  if($pname -eq "cmd" -Or $pname -eq "powershell" -Or $pname -eq "pwsh") {
     Write-Host ("{0}.exe" -f $pname)
     Break
   }

gst-env.py

@@ -549,9 +549,8 @@ def get_windows_shell():
     env = get_subprocess_env(options, gst_version)
     if os.name == 'nt':
         shell = get_windows_shell()
-        if shell == 'powershell.exe':
-            new_args = ['powershell.exe']
-            new_args += ['-NoLogo']
+        if shell in ['powershell.exe', 'pwsh.exe']:
+            new_args = [shell, '-NoLogo']
             if not args:
                 prompt = 'function global:prompt {  "[gst-' + gst_version + '"+"] PS " + $PWD + "> "}'
                 new_args += ['-NoExit', '-Command', prompt]