Add CI environment for bulk Expression Atlas in GCP k8s cluster

[ke4]

We need to create a CI pipeline for Bulk Expression Atlas, a similar one that we already have for Single Cell Expression Atlas.
This would help us to execute all our tests whenever we are working on a new feature / bug and making a Pull Request.

The list of tasks related to this EPIC:

• Config file for Jenkins that creates a POD for Bulk's CI pipeline
• Define the Jenkinsfile for the execution of the pipeline for Bulk Expression Atlas CI
• Create volume claims for Bulk Expression Atlas in GCP k8s cluster
• Create and populate PostgreSQL DB for Bulk Expression Atlas CI
• Create and populate Solr Cloud for Bulk Expression atlas CI
• Update README for the atlas-k8s-ci-environment repository

Take the scripts in prepare-dev-environment in bulk Expression Atlas and add a set of K8s manifests to create a pre-populated SolrCloud cluster and experiment design volumes, etc. to run CI tests in bulk and atlas-web-core.

In the repository https://github.com/ebi-gene-expression-group/atlas-k8s-ci-environment create a directory that contains all the bulk YAML files and a README.md with instructions.

[ke4]

We started to add the Jenkins config files with @alfonsomunozpomer .
Here is the PR: #158

[ke4]

I started to add the yaml config files for gxa-data and gxa-solrcloud in https://github.com/ebi-gene-expression-group/atlas-k8s-ci-environment repository.
Here is the PR: [Chore] Create CI env in Jenkins for bulk Expression Atlas in GCP k8s cluster #3