Support `CompletionEntry.isRecommended` from TypeScript

[mjbvz]

Feature request
TS 2.7 adds a new isRecommended property on CompletionEntry (microsoft/TypeScript#20020) This is marked so we can figure out that a type makes sense in a given location. We should observe this property in VS Code to order our completions

[jrieken]

Verified, however it does conflict with how we memorise suggestions.... @mjbvz Maybe we shouldn't change the sorting but expose something like selectedCompletionIndex on the CompletionResult. That's hard to merge, in case of multiple providers and multiple occurrences, but worth a try.

[mjbvz]

@jrieken Yes actually suggest memory messes up other sorting smartness like #40311 as well

Could we could borrow the TS concept of isRecommended on completion items?

[jrieken]

Yeah, we can think of exposing something in the API and that will then over-rule the memory. Not sure if a boolean is the best (as it allow all items to be recommended)