feat(improve): Remove scan through globals

[aakoshh]

Description

Problem*

Resolves #5001

Summary*

Removes the search for a global by local module ID and name when elaborating a global variable declaration. Instead simply looks up the global by the ID that we have in the definition we are elaborating. In fact the elaboration starts from a global ID of an unresolved global.

I could be way off the mark on whether this is the right thing to do.

Additional Context

I found a couple of things odd:

• NodeInterner::push_global pushes a DefinitionKind::Global(id) with the exact ID that the GlobalInfo will have, ie. it is self-referential (just an observation). This is called during the collection of unresolved globals.
• Elaborator::add_global_variable_decl only looks for globals by local_id and name, but not by definition, even though at this point we know that the definition must contain a GlobalId, otherwise we would have stayed in Elaborator::add_variable_decl.
• if a global cannot be found, it calls NodeInterner::push_definition with the definition in the parameters; since we know it contains a GlobalId and that the same ID must have been inserted in push_global as well, it will now be part of two definitions at different locations - not sure exactly what this means or looks like in code

I added some assertions in the commits to check that during the tests on CI, the global_id and the definition, and any results found by the lookup by local+name, are always consistent, which is why in the end I thought that if the only thing we can find is the one we can get by ID, why not get just get it?

Documentation*

Check one:

• No documentation needed.
• Documentation included in this PR.
• [For Experimental Features] Documentation to be submitted in a separate PR.

PR Checklist*

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.

[michaeljklein]

LGTM

[jfecher]

👍