Always push namespace onto the stack

[st0012]

Motivation

Found this when working on visibility tracking: Currently, the indexer doesn't index classes and modules that have dynamic namespace. Similarly, those classes and modules' names are not pushed onto the namespace stack. However, the stack is currently popped on every class or module exit, which could lead to an incorrect stack popping.

Implementation

This PR fixes the issue by always pushing the namespace to the stack, even when the namespace is dynamic. This also means that we'll start indexing dynamic namespaces' methods with the correct owner. So it actually enables go-to-definition on dynamic namespaces self-receiver methods too.

Automated Tests

Manual Tests

[vinistock]

I think we actually need to always push and pop the stack. If we don't, we will end up pushing methods into the wrong owner. Consider this

module Foo
  var = Bar
  module var::Baz
    def qux; end
  end
end

If we don't push something into the stack, the qux method will be associated with the Foo module, which is incorrect. I think we can take a similar strategy that we used for code lens.

If we find a dynamic declaration, we can either push something into the stack that we can easily identify like <dynamic declaration> or use some boolean to remember we're inside a dynamic context. Then we need to discard every method definition we encounter while we're in a dynamic declaration.

[st0012]

@vinistock I've updated the implementation to always push to the stack.