Run "slow" tests as part of pull request checks

The execution of this check takes less than 15 minutes, which is well
below our overall CI time for pull requests (around 45 minutes). Making
these tests part of pull request checks will ensure we catch problems
early.

.github/workflows/slow-tests.yml

@@ -1,14 +1,14 @@
 # Copyright Kani Contributors
 # SPDX-License-Identifier: Apache-2.0 OR MIT
 
-# We use block scalar notation to allow us to add ":" to the workflow name.
-name: >-
-  Nightly: Slow tests
-
+name: Slow tests
 on:
-  schedule:
-    - cron: "30 5 * * *" # Run this every day at 05:30 UTC
-  workflow_dispatch:     # Allow manual dispatching for a custom branch / tag.
+  pull_request:
+  push:
+    # Not just any push, as that includes tags.
+    # We don't want to re-trigger this workflow when tagging an existing commit.
+    branches:
+      - '**'
 
 env:
   RUST_BACKTRACE: 1