Add resource shrinker sources to R8 repo

This is a verbatim copy for now since this will allow us to easily
merge in either direction - downside is that this does not pass our formatter.

I have added 8.2.20-dev to third_party/r8 to allow us to compile this standalone, this is not used when compiled into r8 (in a follow up). We should be able to refactor the setup to eventually not need this hack.

Add build setup in new gradle build files

Bug: 287398085
Change-Id: Ib9ab46acb67dc4d713e91b82f27b30ef67fb065a
diff --git a/d8_r8/settings.gradle.kts b/d8_r8/settings.gradle.kts
index 77ad2e0..a02c904 100644
--- a/d8_r8/settings.gradle.kts
+++ b/d8_r8/settings.gradle.kts
@@ -50,6 +50,7 @@
 // This project is temporarily located in d8_r8. When moved to root, the parent
 // folder should just be removed.
 includeBuild(root.resolve("keepanno"))
+includeBuild(root.resolve("resourceshrinker"))
 
 // We need to include src/main as a composite-build otherwise our test-modules
 // will compete with the test to compile the source files.