Upgrade to latest protobuf gradle plugin

- Update source jars to use a lazy api to retrieve source
  directories
- Use updated way to add protobuf generated code into sources

Test: ./gradlew bOS --dry-run
Change-Id: Ifcb540b44dfe73ba2efb195566997ac2d5342291
diff --git a/glance/glance-wear-tiles/build.gradle b/glance/glance-wear-tiles/build.gradle
index cd8d37f..7c09cd6 100644
--- a/glance/glance-wear-tiles/build.gradle
+++ b/glance/glance-wear-tiles/build.gradle
@@ -77,6 +77,8 @@
     lintOptions {
         // TODO(b/191286558): Remove when lint is fixed.
         disable "UnsafeOptInUsageError", "UnsafeOptInUsageWarning"
+        // protobuf generates unannotated methods
+        disable "UnknownNullness"
     }
 
     sourceSets {