Treat R8 warnings as failures for system_server

Treating warnings as failures avoids unexpected issues at build and
runtime, particularly for missing class references. Unblock this by
adding explicit top-level references to several stub classes, and
suppressing a warning for optional jacococ class references (guarded
by a runtime check in CoverageService).

Test: m services (also w/ EMMA_INSTRUMENT(_FRAMEWORK)=true)
Bug: 242088131
Change-Id: Iee02a30eeccdcf785e90438d1557867ffda659e7

services/Android.bp

@@ -58,6 +58,7 @@ system_optimized_java_defaults {
                 // retracing infra.
                 optimize: false,
                 shrink: true,
+                ignore_warnings: false,
                 proguard_flags_files: ["proguard.flags"],
             },
             // Note: Optimizations are disabled by default if unspecified in
@@ -174,6 +175,8 @@ java_library {
         "android.hidl.manager-V1.0-java",
         "framework-tethering.stubs.module_lib",
         "service-art.stubs.system_server",
+        "service-permission.stubs.system_server",
+        "service-sdksandbox.stubs.system_server",
     ],
 
     // Uncomment to enable output of certain warnings (deprecated, unchecked)

services/proguard.flags

@@ -118,3 +118,7 @@
 -keep,allowoptimization,allowaccessmodification class com.android.server.usage.StorageStatsManagerLocal { *; }
 -keep,allowoptimization,allowaccessmodification class com.android.internal.util.** { *; }
 -keep,allowoptimization,allowaccessmodification class android.os.** { *; }
+
+# CoverageService guards optional jacoco class references with a runtime guard, so we can safely
+# suppress build-time warnings.
+-dontwarn org.jacoco.agent.rt.*