etcd v3.7 Docker image deprecations

### What would you like to be added?

Hi

I would like the project to announce the following changes from etcd 3.7+ onwards:

1. etcd images are now available at `registry.k8s.io/etcd`. Please update your manifests to pull from there. Lets update the previous github releases.
2. `gcr.io/etcd-development` & `quay.io/etcd` are now deprecated, and we will no longer push etcd 3.8 and newer versions there
3. per arch specific tags, such as `etcd:v3.7.0-amd64` are now deprecated and will no longer be pushed, please switch to the main tagged version as it is a multi-architecture image. This one we can apply in 3.7
4. etcd has been available to download from GitHub releases for several releases. We will also stop publishing to https://storage.googleapis.com/etcd, so please ensure you download etcd from our GitHub releases page.

During 3.6, I'll be working on fixing the release pipeline and making it fully automated #20915

### Why is this needed?

etcd is now a Kubernetes project, and the designated methods for serving release assets are:
- images are served from `registry.k8s.io`
- blobs are served from GitHub releases

Start by reviewing the repository's manifests and the release pipeline work referenced in #20915. Check how image registries, architecture-specific tags, and release asset URLs are currently configured. Done means manifests use registry.k8s.io/etcd and GitHub releases, deprecated registries and per-architecture tags are no longer relied on, and the release process reflects these changes.

Written by the indexing model from the issue text.