Alias studiow to ./gradlew studio, clean up related plumbing

Moves our forked studio_versions.properties StudioVersions.kt
Moves agp / kotlin fork logic to build_dependencies.gradle

Test: ./gradlew studio from both root and ui projects
Change-Id: I4a712f7b1a688dc9e9b7a1119a6c6450357fc110

diff --git a/build.gradle b/build.gradle
index c848e04..e814436 100644
--- a/build.gradle
+++ b/build.gradle

@@ -32,7 +32,7 @@
     SdkHelperKt.setSdkInLocalPropertiesFile(ext.supportRootFolder)
 
     dependencies {
-        classpath build_libs.gradle
+        classpath build_libs.agp
         classpath build_libs.kotlin.gradle_plugin
         classpath build_libs.dokka_gradle
     }