patch 8.2.3079: Powershell core not supported by default

Problem:    Powershell core not supported by default.
Solution:   Set option defaults for "pwsh". (Mike Williams, closes #8481)
diff --git a/src/os_win32.c b/src/os_win32.c
index 1a005c9..eff2269 100644
--- a/src/os_win32.c
+++ b/src/os_win32.c
@@ -2135,6 +2135,7 @@
     char_u	*pathbuf = NULL;
     char_u	*pathext = NULL;
     char_u	*pathextbuf = NULL;
+    char_u	*shname = NULL;
     int		noext = FALSE;
     int		retval = FALSE;
 
@@ -2142,8 +2143,10 @@
 	return FALSE;
 
     // Using the name directly when a Unix-shell like 'shell'.
-    if (strstr((char *)gettail(p_sh), "powershell") == NULL
-				&& strstr((char *)gettail(p_sh), "sh") != NULL)
+    shname = gettail(p_sh);
+    if (strstr((char *)shname, "sh") != NULL &&
+	!(strstr((char *)shname, "powershell") != NULL
+				    || strstr((char *)shname, "pwsh") != NULL))
 	noext = TRUE;
 
     if (use_pathext)