and use it in blockstorage.cpp
PR rationale:
> Seems confusing to pass chainparams to each method individually, when the params can't change anyway for the whole lifetime of the block manager, and also must be equal to the ones used by the chainstate manager.
>
> Fix this issue by removing them from the methods and instead storing a reference once in a member field.
This is a partial backport of [[https://github.com/bitcoin/bitcoin/pull/27570 | core#27570]]
https://github.com/bitcoin/bitcoin/pull/27570/commits/facdb8b331da17c10b122deb28f6d71d5797f063
(partial) https://github.com/bitcoin/bitcoin/pull/27570/commits/fa5d7c39eb992467e43b12db213b27913374fb83
Depends on D16010