Return updated items in resolve* operations

[AlexTugarev]

at least with latest monaco 0.12.0 the resolution of suggestion items is broken in some cases. it can be reproduced with JDT LS, when you continue typing a prefix of a suggestion shown after the suggestions were triggered explicitly. it happens that the completion/resolve params are missing a data field.

the actual issue is, that monaco looses information, because the CompletionItemProvider won't fill up the given item, but returns a new one, which is the converted result from LS.

monaco's SuggestAdapter, which calls the completion item provider, will just update the given suggestion item and overwrites such additional fields, if they are not preserved by LSs.

reading the docs and looking at other CompletionItemProvider implementations, shows that it's OK to return the given item, which can be updated with more data from LS response.

		/**
		 * Given a completion item fill in more data, like [doc-comment](#CompletionItem.documentation)
		 * or [details](#CompletionItem.detail).
		 *
		 * The editor will only resolve a completion item once.
		 *
		 * @param item A completion item currently active in the UI.
		 * @param token A cancellation token.
		 * @return The resolved completion item or a thenable that resolves to of such. It is OK to return the given
		 * `item`. When no result is returned, the given `item` will be used.
		 */
		resolveCompletionItem?(item: CompletionItem, token: CancellationToken): ProviderResult<CompletionItem>;

the resolution of CodeLenses is also broken with JDT LS.

[rcjsuen]

What you described makes sense to me and the changes look good, Alex. Thanks!

[akosyakov]

@AlexTugarev thank you, please merge