build: Use shared workflows

Use shared workflows from https://github.com/canonical/identity-credentials-workflows instead of repeating the same workflows in each project.

This is a first step, and only includes the workflows that were trivial to migrate. More complex workflows that would require parameterization have not been migrated.

.github/workflows/main.yaml

@@ -17,13 +17,13 @@ concurrency:
 jobs:
 
   build:
-    uses: ./.github/workflows/build-rock.yaml
+    uses: canonical/identity-credentials-workflows/.github/workflows/build-rock@main
 
   scan:
     needs: build
-    uses: ./.github/workflows/scan-rock.yaml
+    uses: canonical/identity-credentials-workflows/.github/workflows/scan-rock@main
 
   publish:
     if: github.ref_name == 'main'
     needs: [scan, build]
-    uses: ./.github/workflows/publish-rock.yaml
+    uses: canonical/identity-credentials-workflows/.github/workflows/publish-rock@main