Add "forEachByte" variant to DataBuffer for efficient traversing

[bclozel]

As seen in #34651, iterating over bytes in NettyDataBuffer is not efficient and we should offer a dedicated variant for processing bytes in a DataBuffer without going through bound checks for every byte.

This can be a default method for most implementations and use the optimized variant for Netty ByteBuf.

[github-actions]

Fixed via ee284f2