Adds the ability to declare a module as *private*. Modifies the parser to add the `private` keyword as a reserved keyword. All the checks for private modules are implemented as an independent *Compiler pass*. No checks are done at runtime.
# Important Notes
- Introduces new keyword - `private` - a reserved keyword.
- Modules that have `private` keyword as the first statement are declared as *private* (Project private)
- Public module cannot have private submodules and vice versa.
- This would require runtime access checks
- See #7088 for the specification.
