[monorepo] avoid corepack network requests (#33502)

* [monorepo] avoid corepack network requests

- Download yarn via corepack as the first step in all the docker files
- Turn off networking in corepack
- Do not run things in the upstream node image
  Instead, use the monorepo image, or base layer in all the services.
- Always build the base layer when running tests (uses cache)

* [monorepo] install corepack in shared place

* [clsi-lb] remove unrelated changes

* [web] add missing DC_RUN_FLAGS

* [monorepo] only rebuild test images locally

Also remove spurious build config in docker-compose.ci.yml.

* [server-ce] test: make yarn files available to host-admin and e2e

* [monorepo] put the corepack install snippet in a few more places

GitOrigin-RevId: 38005016ae5a708e12295e246269d6c18fece937

server-ce/Dockerfile-base

@@ -33,7 +33,6 @@ RUN --mount=type=cache,target=/var/cache/apt,sharing=locked \
 &&  echo "deb [signed-by=/etc/apt/keyrings/nodesource.gpg] https://deb.nodesource.com/node_22.x nodistro main" | tee /etc/apt/sources.list.d/nodesource.list \
 &&  apt-get update \
 &&  apt-get install -y nodejs \
-&&  corepack enable \
     \
 &&  rm -rf \
 # We are adding a custom nginx config in the main Dockerfile.