Add Get-Runspace compatibility function for PS v3/v4 (#9731)

Author: potatoqualitee

opt/Get-Runspace.ps1

@@ -0,0 +1,23 @@
+if (-not $ExecutionContext.SessionState.InvokeCommand.GetCommand('Get-Runspace','Function,Cmdlet')) {
+    function Get-Runspace {
+        try {
+            $runspaces = [Dataplat.Dbatools.Runspace.RunspaceHost]::Runspaces.Values
+            foreach ($rs in $runspaces) {
+                $availability = switch ($rs.State.ToString()) {
+                    'Running' { 'Available' }
+                    default   { 'NotAvailable' }
+                }
+                [PSCustomObject]@{
+                    Id           = $rs.RunspaceGuid
+                    Name         = $rs.Name
+                    Type         = $rs.GetType().Name
+                    State        = $rs.State
+                    Availability = $availability
+                    InstanceId   = $rs.RunspaceGuid
+                }
+            }
+        } catch {
+            Write-Warning "Unable to enumerate dbatools-managed runspaces: $_"
+        }
+    }
+}