These services currently live in core/; however, they operate on the
ledger. Mores so, these two services operate on the blockstore only,
and not necessarily the entire ledger. So, it makes sense to move these
services out of core and into ledger. We've recently been doing similar
changes with breaking things out into individual crates in order to
reduce the scope of core.
So, this change moves the services from core/ to ledger/, and replaces
ledger with blockstore.
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