perf: direct access to serialize method

[cesco69]

Direct access to serialize method (eg.: asString(key)) instead of access to object/method (eg.: serializer.asString(key))

Maybe faster...?

Side note: I can't run benchmark/test in local... If try to create a new branch and/or run test I see this error: t.plan is not a function

  duration_ms: 0.2367
  location: 'D:\\fast-json-stringify\\test\\additionalProperties.test.js:112:1'
  failureType: 'testCodeFailure'
  error: 't.plan is not a function'
  code: 'ERR_TEST_FAILURE'
  name: 'TypeError'
  stack: |-
    TestContext.<anonymous> (D:\fast-json-stringify\test\additionalProperties.test.js:113:5)
    Test.runInAsyncScope (node:async_hooks:203:9)
    Test.run (node:internal/test_runner/test:631:25)
    Test.processPendingSubtests (node:internal/test_runner/test:374:18)
    Test.postRun (node:internal/test_runner/test:715:19)
    Test.run (node:internal/test_runner/test:673:12)
    async Test.processPendingSubtests (node:internal/test_runner/test:374:7)

Please add benchmark TAG