gh-99941: asyncio.Protocol.data_received now received immutable bytes

[DarioDaF]

Made asyncio.Protocol.data_received receive immutable object
bytes instead of bytearrays (like defined in the docs) with regression tests added
and opted to use memoryview to take the slices for performance on big buffers.

Performance test from #21442 done on my machine with 10
repetitions on release build with timings 0.043 (delta: 0.019) before patch
and 0.041 (delta: 0.010) after so no noticable change in performance.

• Issue: asyncio tcp transport on Windows reads bytearray instead of bytes #99941

[cpython-cla-bot]

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[kumaraditya303]

@gvanrossum Is this what you intended? I thought that we were going for a documentation update and some unittests though I might be misunderstanding. If this is to be accepted then we need more benchmarks with larger payloads to verify.

[gvanrossum]

Just some nits for the news entry. I'll apply that and then merge.