feat: add stop lifecycle hook for external providers

Provider-backed services were silently skipped on `docker compose stop`,
leaving external resources running after the user expected the stack to
be paused (e.g. after Ctrl+C during `up --watch`).

Compose now invokes `<provider> compose stop <service>` for providers
that advertise a `stop` block in their `metadata` subcommand output.
Providers that do not advertise stop (or do not implement metadata at
all) are silently skipped, preserving backward compatibility with
existing providers that pre-date this hook.

Closes #13772

Signed-off-by: Guillaume Lours <glours@users.noreply.github.com>