[Proposal] Improving access modifiers. in/out namespace

[jarogor]

Improving access modifiers, extending them to nemspaces. Using in/out modifiers for namespaces to check the right to inject into it from the top or from it to the top at the compilation stage.

This will allow writing in one project what is currently divided into different projects. This will replace tools like ArchUnitNET and transfer part of the control to compilation and analysis in the IDE.

Example:

in namespace

You can import into it, but not from it:

in namespace Foo;

out namespace

You can import from it, but not into it:

out namespace Bar;

Without specifying in/out, both are allowed and everything works as usual.

[HaloFour]

See: #8654