Make classes visibly initialized faster.

Reduce the batch size from 32 to 16 and the trigger count
from 1024 to 128.

This may help system health micro-benchmarks (b/138601570)
but I'm unable to run the forrest tests locally to verify.

Bug: 138601570
Bug: 36692143
Test: m
Change-Id: I4d938ddbd284ebe624d146eca9ad59ceefeba4d4
diff --git a/runtime/class_linker.cc b/runtime/class_linker.cc
index a79b87d..33016a2 100644
--- a/runtime/class_linker.cc
+++ b/runtime/class_linker.cc
@@ -312,7 +312,7 @@
     }
   }
 
-  static constexpr size_t kMaxClasses = 32;
+  static constexpr size_t kMaxClasses = 16;
 
   ClassLinker* const class_linker_;
   size_t num_classes_;