Rework symbol visibility checking to allow for multiple potential containers

[Wesley Wigham (weswigham)]

Eg, in the case of

namespace Foo {
   export interface Bar {}
}
export = Foo;

as far as symbol visibility is concerned, Bar has two containing symbols - the Foo namespace (which is what is reported today, as the Bar symbol's .parent) and the file the Foo namespace is assigned to (as it will appear as an (indirect) export of it). This implies there are two equally valid ways to qualify an access to it - Foo.Bar or import("./foo/path").Bar, the first only being valid internally, while the second is always valid.

Fixes #24666