[CI] Add proof-manager-cli to docker context for docker files with cargo.toml dep

Summary:
Now that cargo.toml also includes this, we need it in the docker context for apps that include cargo.toml

Perhaps we should just include the whole monorepo for everything, but it is best practice to only include what you need for the build.

Test Plan: docker build -f ecash-herald.Dockerfile -t ecash-herald_local . etc

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D18634