Limit number of storage maps per account to 64

As motivated in https://github.com/0xMiden/node/issues/2121#issuecomment-4527244793, we should limit the number of storage maps per account to 64.

For now, storage can only be set at account creation time, so we only need to assert this then. We can compute the number of storage maps in `$kernel::account::insert_new_storage` and assert it is <= 64.

On the Rust side, we should also validate this in `AccountStorage`. We can add a constant:

```rust
impl AccountStorage {
pub const MAX_NUM_STORAGE_MAPS: usize = 64;
}
```

And then add validation in `AccountStorage::new`.