Introduce -Xoutput-imports mode of JVM compiler

In this mode, instead of analyzing files and generating bytecode for
them, compiler just saves imports of each file in JSON map of form

'<path to file> -> [<import1>, <import2>, ...]'

It is needed for some external tools, notably for Google3 toolchain.

compiler/tests/org/jetbrains/kotlin/cli/CliTestGenerated.java

@@ -221,6 +221,12 @@ public class CliTestGenerated extends AbstractCliTest {
             runTest("compiler/testData/cli/jvm/help.args");
         }
 
+        @TestMetadata("importsProducer.args")
+        public void testImportsProducer() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/cli/jvm/importsProducer.args");
+            doJvmTest(fileName);
+        }
+
         @TestMetadata("inlineCycle.args")
         public void testInlineCycle() throws Exception {
             runTest("compiler/testData/cli/jvm/inlineCycle.args");