[AllOpen] Reorganize module structure of AllOpen plugin

This scheme will be common for all compiler plugins with K1 and K2 support:
- `plugin-common` contains classes shared with K1 and K2 implementations (if any)
- `plugin-k1` contains implementation for K1 compiler
- `plugin-k2` contains implementation for K2 compiler
- `plugin-backend` contains implementation for backend extensions (if any)
- `plugin-cli` is module for registration of plugin in CLI compiler
- `plugin` is a root module with tests and all submodules embedded

This structure is needed to distinguish parts related to different frontends,
  which is needed for proper dependencies settings for Kotlin IDE plugins

plugins/allopen/testData/bytecodeListing/anonymousObject.txt

@@ -0,0 +1,47 @@
+@java.lang.annotation.Retention(value=RUNTIME)
+@kotlin.Metadata
+public annotation class AllOpen {
+    // source: 'anonymousObject.kt'
+}
+
+@kotlin.Metadata
+public final class Test$a$1 {
+    // source: 'anonymousObject.kt'
+    enclosing method Test.<init>()V
+    inner (anonymous) class Test$a$1
+    method <init>(): void
+    public method run(): void
+}
+
+@kotlin.Metadata
+public final class Test$b$1 {
+    // source: 'anonymousObject.kt'
+    enclosing method Test.b()V
+    inner (anonymous) class Test$b$1
+    method <init>(): void
+    public method run(): void
+}
+
+@kotlin.Metadata
+final class Test$b$2 {
+    // source: 'anonymousObject.kt'
+    enclosing method Test.b()V
+    public final static field INSTANCE: Test$b$2
+    inner (anonymous) class Test$b$2
+    static method <clinit>(): void
+    method <init>(): void
+    public final method run(): void
+}
+
+@AllOpen
+@kotlin.Metadata
+public class Test {
+    // source: 'anonymousObject.kt'
+    private final @org.jetbrains.annotations.NotNull field a: java.lang.Runnable
+    inner (anonymous) class Test$a$1
+    inner (anonymous) class Test$b$1
+    inner (anonymous) class Test$b$2
+    public method <init>(): void
+    public method b(): void
+    public @org.jetbrains.annotations.NotNull method getA(): java.lang.Runnable
+}