Support TypeScript 2.9 disableSuggestions preference

[mjbvz]

From microsoft/TypeScript#23283

Support the disableSuggestions preference for typescript. You can already hide these errors with "javascript.suggestionActions.enabled": false and "typescript.suggestionActions.enabled": false. This feature would just hook these settings up to typescript so that we don't compute the suggestions if they are not enabled

[mjbvz]

For verification, create a file with an unused variable and try triggering quick fixes for it. None should be returned when javascript.suggestionActions.enabled is false

[roblourens]

I still see this, is it wrong?

[mjbvz]

That's a quick fix instead of a suggestion because there's a warning. Try this in a project that does not have noUnusedLocals set

(Note this setting will also turn of graying out of unused variables)