Direct block body rlp class.

[asdacap]

Is your feature request related to a problem? Please describe.

• Block decoding is so inefficient that doing something like this actually notably improve era import/export.

            int sequenceLength = decoderContext.ReadSequenceLength();

            if (!decoderContext.ShouldSliceMemory)
            {
                byte[] memory = new byte[sequenceLength];
                decoderContext = new Rlp.ValueDecoderContext(memory, sliceMemory: true);
            }

            int blockCheck = decoderContext.Position + sequenceLength;

Describe the solution you'd like

• There should be a class that completely skip decoding the tx's which as far as sync and era/import is concern only need to be re-hashed to calculate tx root.
• This class should use pooled memory and implement IDisposable and replace OwnedBlockBodies.
• Additionally, serving/downloading probably could be better done by using the bodies's byte array directly.
• Note: BlockStore currently store Block, not BlockBody, although it should be relatively easy to decode just the body.

Describe alternatives you've considered

• Do nothing.

Additional context

• Era import although local is actually slightly slower than downloading on a fast internet.

[Ayushdubey86]

can i look into this?

[asdacap]

This is a bit too involved I think