Print Enums Explicitly During cds-typer Run

[daogrady]

Fixes #94

Runtime-enums were formerly derived from the runtime model in their respective index.js file.
This had two drawbacks:

1. importing these files caused a performance hit, as all enums contained in that file were dynamically built -- even if they were not being used.
2. the cds minimizer would remove all enums from the runtime model that were not referenced anywhere in the model. If the user wanted to have those enums even if they went unused in the model, they would run into a runtime error (see [BUG] App crashes with unused enum types #94)

So the former

module.exports.MyEnum = Object.fromEntries(Object.entries(cds.model .......))

now becomes

module.exports.MyEnum = { A: 'a', B: 'b', ... }