Python: bytearray body support for ASGI module.

@filiphanes requested support for bytearray
and memoryview in the request body here:
<https://github.com/nginx/unit/issues/648>

This patch implements bytearray body support only.
Memoryview body still need to be implemented.

test/test_asgi_application.py

@@ -218,6 +218,14 @@ def test_asgi_application_shm_ack_handle():
     assert resp['body'] == body, 'keep-alive 1'
 
 
+def test_asgi_application_body_bytearray():
+    client.load('body_bytearray')
+
+    body = '0123456789'
+
+    assert client.post(body=body)['body'] == body
+
+
 def test_asgi_keepalive_body():
     client.load('mirror')