CircleCI pipeline utilizes internal Nexus infrastructure

[andrew-jameson]

Description: To fully insulate our pipeline being broken by issues out of our control via upstream issues, we should ensure all steps can be self-sufficient within our infrastructure. For higher environments (HHS repo), we should ensure backwards compatibility with standard internet mirrors

Acceptance Criteria:

• [x] Pipeline builds don't reach out to the internet by default
• [x] Pipeline builds will fail-through to internet repositories if Nexus connection fails
• [x] Pipeline build times are reduced
• [x] Testing Checklist has been run and all tests pass
• [x] README is updated, if necessary

Tasks:

• [x] Apt repo configured
• [x] NPM repo configured
• [x] PyPI repo configured
• [x] Have CloudFoundry CLI be available in the pipeline through Nexus
• [x] Have alternative sources point to our standard internet repositories
• [x] Run Testing Checklist and confirm all tests pass

Notes: Implementation of a base image is out of scope, this is an infrastructure buildout.

Supporting Documentation:

Open Questions:

• How do we build once and reference the docker image moving forward? Out of scope, will generate another docker-nexus ticket.
• How do we correctly cache dependencies/images? Out of scope, will generate another docker-nexus ticket.

[andrew-jameson]

Implemented apt and pypi repositories MVP within #3141