Rename `store::InnerState`

[Mirko-von-Leipzig]

As per #1767 (comment), (and I think general consensus), InnerState is overly vague.

We should move AccountStateForest into InnerState, and find a better name for the latter.

[Mirko-von-Leipzig]

Some ideas off the top of my head.

By backend

files
database
memory

By data

raw_blocks | blocks
database
merkles | trees | ...

[drahnr]

InnerState comes from the fact of wrapping it inside RwLock<_>. I suggest to name it according to something AuxiliaryQueryState which describes the fact we only keep this to serve queries and it's not critical (we could also use ephemeral, but that sounds weird we're going to persist most/all of it)

[bobbinth]

For the blocks/database, I'd probably keep things close to what we have now:

• blocks or block_store.
• db or database.

For the InnerState, it really stores "auxiliary authentication data" (which is all Merkle tree based) - so, I think we could do something like:

• aux_state or auxiliary_state.
• auth_data or auth_state.
• merkle_state or merkle_store.

Out of these, I probably have a slight preference for merkle_store (especially if we keep the block_store for raw block storage). We do have a concept of MerkleStore in the crypto/VM crates which is different - but we don't really use it in the node - so, this name collision may be fine.

So, overall, my top combinations would probably be:

• block_store, db, and merkle_store, or
• block_store, db, and aux_state.