Add "Optimize imports" feature to language service

[cevek]

WebStorm has very helpful feature - Optimize Imports, that just remove unused imports, but doesn't touch barely imports.
Also it merge same module imports into one and sort by import names

import {foo} from './module';
import {bar} from './module';
// optimize to 
import {bar, foo} from './module';

[mhegazy]

Duplicate of #10020