K2: Update reference shortener to handle import alias

The existing reference shortener does not use import alias when it
shortens a symbol. Instead, it adds a new import directive for the
symbol that is already imported. This commit updates reference shortener
to let it reuse the existing import alias rather than adding a new one:

 1. When shortening a symbol, check whether the symbol is already
    imported.
 2. If it is already imported by an import alias, keep the symbol
    reference expression and the import alias as a string together in
    `ShortenCommand`.

The actual PSI update (shortening) based on the ShortenCommand is done
by IntelliJ.

^KTIJ-27205

analysis/analysis-api-impl-base/tests/org/jetbrains/kotlin/analysis/api/impl/base/test/cases/references/AbstractReferenceShortenerTest.kt

@@ -23,6 +23,7 @@ import org.jetbrains.kotlin.test.services.assertions
  * Note that it tests shortening only a single expression between <expr> and </expr> in the first file.
  */
 abstract class AbstractReferenceShortenerTest : AbstractAnalysisApiBasedSingleModuleTest() {
+
     override fun doTestByFileStructure(ktFiles: List<KtFile>, module: TestModule, testServices: TestServices) {
         val element = testServices.expressionMarkerProvider.getSelectedElementOfType<KtElement>(ktFiles.first())
 

analysis/analysis-api-impl-base/tests/org/jetbrains/kotlin/analysis/api/impl/base/test/cases/references/ShorteningResultsRenderer.kt

@@ -14,14 +14,14 @@ internal object ShorteningResultsRenderer {
             return
         }
 
-        shortening.typesToShorten.forEach { userType ->
+        shortening.listOfTypeToShortenInfo.forEach { (userType, shortenedRef) ->
             userType.element?.text?.let {
-                appendLine("[type] $it")
+                appendLine("[type] $it${shortenedRef?.let { ref -> " -> $ref" } ?: ""}")
             }
         }
-        shortening.qualifiersToShorten.forEach { qualifier ->
+        shortening.listOfQualifierToShortenInfo.forEach { (qualifier, shortenedRef) ->
             qualifier.element?.text?.let {
-                appendLine("[qualifier] $it")
+                appendLine("[qualifier] $it${shortenedRef?.let { ref -> " -> $ref" } ?: ""}")
             }
         }
         shortening.kDocQualifiersToShorten.forEach { kdoc ->