Add task to install all requirements of an integration (#108262)

* Add task to install the requirements of an integration

* Gather recursive requirements

* Move valid_integration to util

* Apply suggestions from code review

Co-authored-by: Marc Mueller <30130371+cdce8p@users.noreply.github.com>

* Implement suggestions

---------

Co-authored-by: Marc Mueller <30130371+cdce8p@users.noreply.github.com>

script/util.py

@@ -0,0 +1,15 @@
+"""Utility functions for the scaffold script."""
+
+import argparse
+
+from .const import COMPONENT_DIR
+
+
+def valid_integration(integration):
+    """Test if it's a valid integration."""
+    if not (COMPONENT_DIR / integration).exists():
+        raise argparse.ArgumentTypeError(
+            f"The integration {integration} does not exist."
+        )
+
+    return integration