Refactor reading doo manifest from Backend to AST

[ShubhamChaturvedi7]

Dafny version

4.6

Code to produce this issue

N/A

Command to run and resulting output

N/A

What happened?

This is the discussion from the Go Module PR: #5140

@robin-aws : I definitely don't love having a code generator re-read assets from the file system, it feels like that's going to bite us in the future. But I also appreciate this is much easier than attaching doo file metadata to the AST. Can we cut an issue to revisit?

What type of operating system are you experiencing the problem on?

Other