Etcd v3.5.7 or later no longer ships with a shell in the default image.

Currently in the following clustermesh-apiserver deployment, we rely on the availability of a shell:

In order to bump the etcd dependency to v3.5.7, we need to update this line to either:

1. Rely on another image that has a shell that we can use in order to configure etcd, OR
2. Rework these instructions such that they work directly in the etcd 3.5.7 container.

Related: #23760