message: Add `TraceContext` to register allocation
  Summary: Allows filtering the detailed stream of allocation info.
diff: @@ -32,6 +32,7 @@ Stats allocate(const Config& allocator_config, DexMethod* m) {
  if (m->get_code() == nullptr) {
  return Stats();
  }
  + TraceContext context(m);
  auto& code = *m->get_code();
  auto scoped = at_scope_exit([&code]() { code.clear_cfg(); });
  TRACE(REG, 5, "regs:%d code:\n%s", code.get_registers_size(), SHOW(&code));
  