Replace isModule with ModuleOrNamespaceKind in SynModuleOrNamespace

[auduchinok]

Storing kind removes some workarounds used by FCS clients for checking whether a module is anonymous and whether a namespace is global.

Adds the following type to replace isModule: bool fields.

[<Struct>]
type SynModuleOrNamespaceKind =
    | NamedModule
    | AnonModule
    | DeclaredNamespace
    | GlobalNamespace

[auduchinok]

I updated structure tests. Despite having the following comment implicit modules ranges were returned in structure service:

// do not return range for top level implicit module in scripts

Checking AnonModule kind only makes Structure service not return these ranges for source files as well. Would this behaviour be expected or do we want to get folding ranges for implicit modules in source files and not get them in scripts? I'd prefer the same behaviour of not getting these ranges.

I also added cases for explicit module and namespace cases there.

[TIHan]

The check should probably be kind = NamedModule since we don't want to include namespaces?

I think you might be right that we should have the same behavior for anon modules in scripts and non-scripts.

[auduchinok]

I don't mind having an option to fold a namespace but it would require fixing folding ranges in Structure provider which is better to have in a separate PR. Thanks, I'll replace the check.

[auduchinok]

I don't see a reason to fold a top level module, though, as we can't have other modules/namespaces below it.

[TIHan]

I like the PR. It makes sense that we have a SynModuleOrNamespaceKind to represent the different namespaces and modules that we have.

[auduchinok]

It seems to be ready.
cc @nojaf @jindraivanek @nosami @Krzysztof-Cieslak

[TIHan]

Looking at this again, why are some of these ranges removed from the tests? It looks like it was giving you the range of the whole module itself.

[auduchinok]

It's removing ranges of anon top level modules.

[TIHan]

I see, yes that makes sense. That's just an inner module.

[dsyme]

Oh that's nice

[TIHan]

Thank you