Rename ArenaAllocator -> Arena

benchmarks/bench_metric.cpp

@@ -1,6 +1,6 @@
 #include <nanobench.h>
 
-#include "arena_allocator.hpp"
+#include "arena.hpp"
 #include "metric.hpp"
 
 #include <atomic>
@@ -62,7 +62,7 @@ struct ContentionEnvironment {
     render_latch = std::make_unique<std::latch>(2);
 
     background_threads.emplace_back([this]() {
-      ArenaAllocator arena;
+      Arena arena;
 
       render_latch->arrive_and_wait(); // Render thread signals it's ready
 
@@ -201,7 +201,7 @@ int main() {
             });
       }
 
-      ArenaAllocator arena;
+      Arena arena;
       std::string bench_name =
           "render() - " + std::to_string(scale) + " metrics each type";