Decouple Jest packages from the Roblox datamodel

[grilme99]

Before Jest can run in Lua environments other than Roblox's, it has to be decoupled from the Roblox datamodel. Primarily, this means:

• All require calls should have their Instance paths replaced with file system strings.
• Darklua should be used during the build/release pipeline to convert the string requires back to Instances for Roblox users.
• Once the string requires work and pass all tests, internal structures in Jest should then be decoupled from the datamodel. This is a much larger effort, as Roblox changed all file system references to their datamodel equivalent. Whatever solution we come up with here needs to be backwards-compatible for Roblox users. All environments must be supported (command line and Roblox).

This is a major goal for this project, as many Lua users outside of Roblox would benefit from the full Jest testing suite. Contributors are welcome and appreciated for parts of this issue.