protobuf: add arena allocation with cleanup benchmark

Allocation with cleanup is quite different from the normal allocation.
Add a synthetic benchmark for it.

PiperOrigin-RevId: 561272213

php/ext/google/protobuf/php-upb.c

@@ -1,6 +1,8 @@
 /* Amalgamated source file */
 #include "php-upb.h"
 
+test-xyz
+
 /*
  * This is where we define internal portability macros used across upb.
  *

ruby/ext/google/protobuf_c/ruby-upb.c

@@ -1,6 +1,8 @@
 /* Amalgamated source file */
 #include "ruby-upb.h"
 
+test-xyz
+
 /*
  * This is where we define internal portability macros used across upb.
  *