build: Pin GitHub Actions

The main benefit of pinning GitHub actions is the determinism it brings
in terms of what version of a given action will be executed. This is
a step towards having hermetic builds.

Once pinned to a commit, dependabot will automatically issue PRs to update
to newer versions.

Pinned versions is the only security metric from OpenSSF scorecard that
this repository currently have a zero score.

Signed-off-by: Paulo Gomes <paulo.gomes@weave.works>

.github/workflows/e2e-bootstrap.yaml

@@ -16,20 +16,20 @@ jobs:
     if: (github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name == github.repository) && github.actor != 'dependabot[bot]'
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@93ea575cb5d8a053eaa0ac8fa3b40d7e05a33cc8
       - name: Restore Go cache
-        uses: actions/cache@v3
+        uses: actions/cache@9b0c1fce7a93df8e3bb8926b0d6e9d89e92f20a7
         with:
           path: ~/go/pkg/mod
           key: ${{ runner.os }}-go1.18-${{ hashFiles('**/go.sum') }}
           restore-keys: |
             ${{ runner.os }}-go1.18-
       - name: Setup Go
-        uses: actions/setup-go@v3
+        uses: actions/setup-go@c4a742cab115ed795e34d4513e2cf7d472deb55f
         with:
           go-version: 1.19.x
       - name: Setup Kubernetes
-        uses: engineerd/setup-kind@v0.5.0
+        uses: engineerd/setup-kind@aa272fe2a7309878ffc2a81c56cfe3ef108ae7d0 # v0.5.0
         with:
           version: v0.16.0
           image: kindest/node:v1.25.2@sha256:9be91e9e9cdf116809841fc77ebdb8845443c4c72fe5218f3ae9eb57fdb4bace