Dockerfile reliant upon requirements.txt and local build

[ppfeister]

Update Dockerfile to build properly with new backend, or pull from PyPI with pip rather than pulling and building from GitHub

[ppfeister]

Should also bump Python version to 3.12 and possibly switch to slim alpine

Add env var SHERLOCK_ENV with value Docker for planned additional support

[ppfeister]

@neolight1010 Looks like you switched this from Alpine to deb a couple years ago. You don't happen to remember what the reason was, do you?

[neolight1010]

Hello! We changed it to Debian to fix some issues with the old Alpine image. In summary, Alpine has horrible performance when used in Python projects. The Debian image turned out smaller and simpler to maintain.

You can check out the details here: #1479

[ppfeister]

@neolight1010 I forgot to hit reply apparently ------ thanks for the extra info! Stuck with deb slim on the fixed image due to those findings.

Somewhat curious now how deb would compare to an rpm type image, but I doubt it's worth putting much time into when this works as well as it does.