Add test to `MerkleDbDataSource` where save is called with unexpected values

[swirlds-automation]

We found some cases where saveRecords(...) is called with negative values for paths and/or empty streams. We should write tests for the different potential inputs and validate the behavior of the DB. Ideally it should be resilient to such things. We don't know how many items are in the stream at the time we try to save.

[swirlds-automation]

_{migrated from:
url=https://github.com/swirlds/swirlds-platform/issues/4526
author:rbair23, #:4526, createdAt:2021-12-14T03:51:52Z, updatedAt=2023-02-22T03:05:37Z
labels=Bug,Platform Virtual Map,Platform Data Structures,RL:Test,Migration:Data}