Adding Dokka source to AOSP

This is taken from commit 4ff3d4153ca344398bffcdaaa28f1a1f6e76f6ad from
https://github.com/google/dokka, which is Google's customized fork of
Dokka (https://github.com/Kotlin/dokka).

Bug: 135767980
Test: ./gradlew :core:cleanTest :core:test
Test: ./gradlew :runners:gradle-integration-tests:clean :runners:gradle-integration-tests:test

Change-Id: I332d0b522706e353c3837f6308aac1a8340d71d3
diff --git a/core/testdata/typealias/deprecated.kt b/core/testdata/typealias/deprecated.kt
new file mode 100644
index 0000000..b53d3a2
--- /dev/null
+++ b/core/testdata/typealias/deprecated.kt
@@ -0,0 +1,7 @@
+package _typealias.deprecated
+
+class Lol
+
+@Deprecated("Not mainstream now")
+typealias Kek = Lol
+