Update subspace for piece cache slot fix

This PR updates subspace to bring in the piece cache slot fix: - https://github.com/autonomys/subspace/pull/3677 We also moved some code around and added new trait methods in `subspace` in: - https://github.com/autonomys/subspace/pull/3660 - https://github.com/autonomys/subspace/pull/3659 - https://github.com/autonomys/subspace/pull/3669 - https://github.com/autonomys/subspace/pull/3678 This PR fixes those imports and adds the new trait methods. It also documents why the security fixes in https://github.com/autonomys/subspace/pull/3660 weren't needed here. ~~It's a draft until all those `subspace` PRs merge, then I'll update the subspace dependency to the main branch. I'm posting it now so these fixes are ready, even if I'm away.~~