feat: using orjson replace ujson

Author: fatelei

CHANGES/10795.feature.rst

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+Added :py:mod:`orjson` support as the default JSON encoder for :py:class:`~aiohttp.ClientSession` and :py:class:`~aiohttp.JsonPayload`.
+When :py:mod:`orjson` is available, it is automatically used instead of the standard library :py:mod:`json` module, providing significantly improved performance for JSON serialization.
+:py:mod:`orjson` is included in the ``speedups`` optional dependency group and can be installed with ``pip install aiohttp[speedups]``.
+The implementation gracefully falls back to :py:mod:`json` when :py:mod:`orjson` is not installed, ensuring backward compatibility.
+Custom JSON encoders can still be provided as before to override the default behavior.
+-- by :user:`fatelei`.