refactor(ci): define configuration variables for multiple workflows

[gustavovalverde]

Motivation

We stopped using secrets for non-sensitive information that could vary in some point in time, as there were some limitations with secrets while using reusable workflows, but GitHub recently added configuration variables to be used in multiple workflows, so we don't have to repeat ourselves: https://github.blog/2023-01-10-introducing-required-workflows-and-configuration-variables-to-github-actions/

Specifications

Documentation: https://docs.github.com/en/actions/learn-github-actions/variables#defining-configuration-variables-for-multiple-workflows

Complex Code or Requirements

Some of the code/variables that needs to be added or changed:

• Our GCP Project name
• Our registry URLs
• GCP machine types
• Other variables that have an impact on all or most workflows

Testing

We must confirm a PR run all test successfully after the change

Related Work

ZcashFoundation/infra#8