Reduce AWS peer discovery workflow run rate

By running it

 * On push, when relevant code paths change
 * Every Monday morning

The peer discovery subsystem does not change
particularly often, and this plugin in particular
does not. Nonetheless, we currently run it for
every push unconditionally.

(cherry picked from commit 893a349)
(cherry picked from commit ac2bbe2)

Author: michaelklishin

.github/workflows/rabbitmq_peer_discovery_aws.yaml

@@ -1,10 +1,12 @@
 name: Peer Discovery AWS Integration Test
 on:
   push:
-    paths-ignore:
-      - '.github/workflows/secondary-umbrella.yaml'
-      - '.github/workflows/update-elixir-patches.yaml'
-      - '.github/workflows/update-otp-patches.yaml'
+    paths:
+      - "deps/rabbitmq_peer_discovery_aws/**"
+      - "deps/rabbitmq_peer_discovery_common/**"
+      - "deps/rabbit/src/rabbit_peer_discovery.erl"
+  schedule:
+    - cron: "4 0 * * MON"
   workflow_dispatch:
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref_name }}