Add JetMultiDeclarationReference

A reference to component* functions
Rewrite optimize imports using JetReference#resolveToDescriptors

 #KT-4451 Fixed
Move, rewrite and rename JetImportOptimizer

Rewrite it to Kotlin and rename to KotlinImportOptimizer, move to imports package
Create ImportsUtils.kt
Optimize Imports tests: Switch to generated approach

Move test and rename test data
Delete unused testdata
Rewrite OptimizeImportOnFlyTest
Optimize Imports: do not keep imports of unimportable entities
Optimize Imports: simplify code