Enhance the outline view in vscode

[jhendrixMSFT]

We use the following tool to populate the outline view in vscode.

https://github.com/ramya-rao-a/go-outline

At present all it provides is package name and top-level functions. Compare this to the outline for say a node program where you get much more information (interfaces, enums, callbacks within funcs etc). At a minimum we should add the following info.

• package-level constants and vars
• interfaces
• structs/typedefs and their associated methods

Once this is working we can investigate if there's any info inside funcs/methods we want to include.

[ramya-rao-a]

When go.useLanguageServer setting is enabled and gopls is used, the outline feature is powered by the language server and it does show more useful information. Any further information we would like to see should be logged as a feature request to gopls in the go issue tracker

There are no plans to enhance the non-language server scenario at the moment, therefore closing this issue.