Use a single connection for data and metadata management

[skejserjensen]

As management of data and metadata using deltalake was developed in parallel, is code and configuration for connecting to, reading from, and writing to object stores of different types duplicated across the modelardb_common/src/storage.rs and modelardb_common/src/metadata modules. This seems unnecessary and a single type for connecting to and performing operations on the object store in ModelarDB should be created.

[CGodiksen]

When combining these into a single type we should also reconsider whether we want to add unit tests for the DeltaLake struct directly or continue to rely on other components testing the functionality indirectly.