CV2-5011 refactors for making alegre dual purpose on text encoding

[DGaffney]

Description

In this ticket, I'm adding functionality for Alegre to serve text encoding responses both in the original, soon-to-be-deprecated way, as well as via presto. Idea is we'll serve both for a bit and slowly work out each individual case to use the new system over time. Insofar as check-api is concerned, we're only slightly modifying alegre_v2.rb to extend use to text. Will need to add a few unit tests to accommodate

References: CV2-5011

How has this been tested?

Tested extensively locally, will need to add unit test coverage for new functions.

Things to pay attention to during code review

None in particular

Checklist

• [ ] I have performed a self-review of my own code
• [ ] I have added unit and feature tests, if the PR implements a new feature or otherwise would benefit from additional testing
• [ ] I have added regression tests, if the PR fixes a bug
• [ ] I have added logging, exception reporting, and custom tracing with any additional information required for debugging
• [ ] I considered secure coding practices when writing this code. Any security concerns are noted above.
• [ ] I have commented my code in hard-to-understand areas, if any
• [ ] I have made needed changes to the README
• [ ] My changes generate no new warnings
• [ ] If I added a third party module, I included a rationale for doing so and followed our current guidelines