[Epic:`.NET`] Introduce new `File` (previously known as `Module`) and `FileMap` ( previously known as `ModuleMap` )

[Daniele Iasella]

Extends the current code-gen-types with a new File and FileMap interfaces and classes to allow generic file content instead of string only

[morhag90]

Passed QA: code generated as expected:

Link to the PR:

morhag90/test#1