Hide underscored attributes by default in Hover, give option to unhide

[award999]

Description

Copying issue from swiftlang/vscode-swift#1729 as we only would expose a setting if we do this.

Is your feature request related to a problem? Please describe.

Describe the solution you'd like
@_rawLayout and @_staticExclusiveOnly should be hidden by default.

Describe alternatives you've considered
Current behavior is fine by me but I don't think it's the best behavior for the average user.

Additional context

[ahoppen]

Ideally, we would render the hover contents using docc from the symbol graph, which should take care of hiding underscored attributes.

[vanshkamra12]

@ahoppen i tried to solve this issue can you please check it...!!!