Ensure consistency of environment checks throughout Next Build

[timcosgrove]

User Story or Problem Statement

We want machine names of environments to be consistent throughout usage of Next Build so that we know we are always using the correct environment.

Description or Additional Context

This PR was created because of a mismatch between the name of the production environment within Next Build and the value that was being passed to it: department-of-veterans-affairs/next-build#863

This highlighted a problem: the environment values that are passed in by the build script - prod staging etc - do not reflect what Next Build itself uses internally - vagovprod, vagovstaging etc.

Next Build should be examined and all references to environment should be made consistent. At a minimum the above indicates that the values passed by the build script need to change to the vagov versions. I'm of the opinion that we should use the vagov versions everywhere, since this is how other teams designate those environments. This is open to discussion however.

Steps for Implementation

Acceptance Criteria

• Testable_Outcome_X
• Testable_Outcome_Y
• Testable_Outcome_Z
• Requires design review
• Requires accessibility review