Move importsDumper to compiler plugin

plugins/imports-dumper/testData/simpleCase/b/B1.kt

@@ -0,0 +1,10 @@
+package b
+
+import a.*
+
+class B1 {
+    companion object {
+        val a1: A1 = A1()
+        val a2: A2 = A2()
+    }
+}

plugins/imports-dumper/testData/simpleCase/b/nestedB/B2.kt

@@ -0,0 +1,7 @@
+package b.nestedB
+
+import a.A1 as AliasedA1
+import a.A1
+
+fun foo(x: AliasedA1): Int = TODO()
+fun bar(x: A1): Int = TODO()