Move append into AccountStorageEntry

[sakridge]

Problem

Seems like AccountStorageEntry object which holds the AppendVec will know when the storage is full or not.

Summary of Changes

Move append into new AccountStorageEntry::append_account function, handle the count and status there.

Fixes #

[sakridge]

@sambley is this right? Seems like we should not update the count when we do insert_account_entry, when we do that in squash. There we increment the count, but we didn't actually append anything, just created another index for it on another fork.

[sambley]

@sambley is this right? Seems like we should not update the count when we do insert_account_entry, when we do that in squash. There we increment the count, but we didn't actually append anything, just created another index for it on another fork.

We would have 2 index entries (one in parent fork and other in squashed fork) both pointing to the same entry as we are not moving it right? The increment was to account for the new index entry being added to the fork.

[sakridge]

@sambley I see, it's like a reference count of all items in the appendvec.