Add proguard to nearby service target.

Also fixed a few minor issues.

Bug: 189355156
Test: install on sunfish && atest NearbyUnitTests
Change-Id: I8f5cc990e69940a48fdad24713015690bdc6d3cd
diff --git a/nearby/service/Android.bp b/nearby/service/Android.bp
index 5b026fa..13dd6a9 100644
--- a/nearby/service/Android.bp
+++ b/nearby/service/Android.bp
@@ -43,6 +43,7 @@
     optimize: {
         enabled: true,
         shrink: true,
+        proguard_flags_files: ["proguard.flags"],
     },
     dex_preopt: {
         enabled: false,