Run integration tests on multipass

There are a few issues running the Longhorn integration tests on an LXD
runner, as we currently are, mainly having to do with ISCSI volumes
being exposed and mounted in LXD.

Running on host has its own issues, mainly the Pods have cluster-wide
connectivity issues.

Instead, we'll be testing Longhorn in a multipass VM. We also remove
some of the GitHub runner's bloat in order to free up sufficient space
for the VM and test. Note that according to the Longhorn deployment
guide, Longhorn requires 25% of the root disk to be available (if no
other disks are available).

.github/workflows/pull_request.yaml

@@ -20,7 +20,7 @@ jobs:
       platform-labels: '{"arm64": ["self-hosted", "Linux", "ARM64", "jammy"]}'
 
   run-tests:
-     uses: canonical/k8s-workflows/.github/workflows/run_tests.yaml@main
+     uses: ./.github/workflows/run_tests.yaml
      needs: [build-and-push-arch-specifics]
      secrets: inherit
      with:

.github/workflows/run_tests.yaml

@@ -0,0 +1,62 @@
+name: Run rocks tests
+
+on:
+  workflow_call:
+    inputs:
+      rock-metas:
+        description: List of maps featuring the built {name, version, path, arch, image}
+        type: string
+        default: "[]"
+
+jobs:
+  run-tests:
+    if: ${{ inputs.rock-metas != '[]' }}
+    name: Run tests
+    runs-on: ubuntu-22.04
+    steps:
+      - name: Maximize build space
+        uses: AdityaGarg8/remove-unwanted-software@v4.1
+        with:
+          remove-android: 'true'
+          remove-haskell: 'true'
+          remove-codeql: 'true'
+          remove-swapfile: 'true'
+      - name: Checkout repository
+        uses: actions/checkout@v4.1.1
+      - name: Setup Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.8'
+      - name: Setup environment
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y jq
+          pip install tox
+      - name: Install multipass
+        run: |
+          set -x
+          sudo snap install multipass
+
+          # We need to authenticate into multipass, since we're not running as root.
+          # https://github.com/canonical/multipass/issues/1437#issuecomment-1435357872
+          sudo multipass set local.passphrase=Passw0rd
+
+          for i in {0..4}; do
+            # If we auth too soon, we might get this error:
+            # authenticate failed: cannot connect to the multipass socket
+            multipass auth Passw0rd && break
+            sleep 1
+          done
+      - name: Run sanity tests
+        env:
+          BUILT_ROCKS_METADATA: ${{ inputs.rock-metas }}
+        run: |
+          tox --conf tests/tox.ini -e sanity
+      - name: Run integration tests
+        env:
+          BUILT_ROCKS_METADATA: ${{ inputs.rock-metas }}
+        run: |
+          export TEST_SUBSTRATE=multipass
+          export TEST_MULTIPASS_MEMORY=6G
+          export TEST_MULTIPASS_DISK=40G
+          tox --conf tests/tox.ini -e integration