tracinglib: remove -Xmulti-platform To integrate better with ASfP, remove KMP usage. Also: - Convert java host test to robolectric - Replace Kotlin 'internal' usage with @VisibleForTesting to reduce duplicate compilation (b/240432457) - Use aconfig flag test capabilities Test: install CoroutineTracingDemoApp Test: atest tracinglib-robo-test Flag: com.android.systemui.coroutine_tracing Bug: 289353932 Change-Id: Ifff786f94765fec844b64716d3f961c9b49d16b9