Backport Blockparts optimitzation if necessary

[evan-forbes]

We should backport https://github.com/cometbft/cometbft/pull/904 if necessary

[cmwaters]

It's not a fix so much as an optimization. It does look like something worth backporting if we don't implement compact blocks first.

This looks like a breaking change so it would have to be released in v2

[faddat]

I think it is a very good idea to backport this.