Move dependency management to pip-compile-multi

[stevejalim]

Description

As part of standarising how we manage our Python deps across MEAO, we're moving to pip-compile-multi

Key tasks

• Revamp dependency management tooling from pip-tools to pip-compile-multi
• Expand Docker setup to allow for a two builds: Dev/test/local-dev build, and a release build, the same as with Bedrock -> Split out to Refactor Docker setup to support separate dev/test and prod images, similar to Bedrock #784

Success critera

• CI passes
• No regression in behaviour/functionality
• Documentation is updated
• Separate documentation site can still be built
• Project can be installed locally with no impediments