Embed the install manifests in flux binary

- add make target for generating the install manifests using kustomize
- embed the generated manifests in flux binary
- the install and bootstrap commands default to using the embedded manifests
- download the install manifests from GitHub only if the install/bootstrap version arg is set

Signed-off-by: Stefan Prodan <stefan.prodan@gmail.com>

.github/workflows/scan.yaml

@@ -27,6 +27,11 @@ jobs:
     if: github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name == github.repository
     steps:
       - uses: actions/checkout@v2
+      - name: Setup Kustomize
+        uses: fluxcd/pkg//actions/kustomize@main
+      - name: Build manifests
+        run: |
+          make build-manifests
       - name: Run Snyk to check for vulnerabilities
         uses: snyk/actions/golang@master
         continue-on-error: true