Switch to Litho snapshot releases

Summary:
This allows breaking changes in Litho to be landed.
I'm also adding some helpers to determine if Flipper itself
is currently in a release or snapshot release train.

N.B. We don't publish snapshot releases for Flipper
right now, but will in the future where this will come in
handy.

Reviewed By: jknoxville

Differential Revision: D9359035

fbshipit-source-id: d21b607eca5d57caf4cc34234f6ba3cb0d8f307d

android/sample/build.gradle

@@ -1,7 +1,6 @@
 apply plugin: 'com.android.application'
 
 android {
-
     compileSdkVersion rootProject.compileSdkVersion
     buildToolsVersion rootProject.buildToolsVersion
     defaultConfig {