[typed store] introduce a way to perform cross column family batch requests

[akichidis]

Currently in order to perform a cross column family batch request, one has to use the DBMap struct to achieve this. An example is shown here: https://github.com/MystenLabs/mysten-infra/blob/e7451bb2d004fa01ef364ad2761bc338c24b1f11/typed-store/src/rocks/mod.rs#L161-L166

however, for codebases that we use the Store struct exclusively for our interaction with the storage, there isn't a way to achieve this.

As part of this issue a way should be implemented to allow us perform cross-column family batch requests.