chore(ci): fix container build (#9765)

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# Which Problems Are Solved

While creating a new release, the [pipeline
failed](https://github.com/zitadel/zitadel/actions/runs/14509737111/job/40705906723)
as GH sunset the old actions cache service:

https://github.blog/changelog/2025-03-20-notification-of-upcoming-breaking-changes-in-github-actions/#decommissioned-cache-service-brownouts

# How the Problems Are Solved

The `driver-opts` parameter is removed from the buildx actions to use
the latest stable image. ([new cache service is used by BuildKit >=
v0.20.0](https://docs.docker.com/build/ci/github-actions/cache/#cache-backend-api))

# Additional Changes

Updated docker/build-push-action to v6 in a first attempt to solve the
issue, but kept it as it gave some more insights (incl. build summary)

# Additional Context

Since the containers are only built on workflow triggers, here's the
corresponding pipeline run:
https://github.com/zitadel/zitadel/actions/runs/14513926232

.github/workflows/container.yml

@@ -53,8 +53,6 @@ jobs:
       - 
         name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
-        with:
-          driver-opts: 'image=moby/buildkit:v0.11.6'
       -
         name: Login to Docker registry
         uses: docker/login-action@v3
@@ -75,7 +73,7 @@ jobs:
       - 
         name: Debug
         id: build-debug
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         timeout-minutes: 3
         with:
           context: .
@@ -90,7 +88,7 @@ jobs:
       - 
         name: Scratch
         id: build-scratch
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         timeout-minutes: 3
         with:
           context: .
@@ -147,8 +145,6 @@ jobs:
       -
         name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
-        with:
-          driver-opts: 'image=moby/buildkit:v0.11.6'
       -
         name: Login to Docker registry
         uses: docker/login-action@v3

.github/workflows/e2e.yml

@@ -31,8 +31,6 @@ jobs:
       -
         name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
-        with:
-          driver-opts: 'image=moby/buildkit:v0.11.6'
       -
         name: Start DB and ZITADEL
         run: |