multidb: change tables map to map[string]larry.database

# Issue
Currently, MultiDB accepts a map[string]string to initialize each table as a separate database. This requires manually integrating each database type into the MultiDB package, and prevents more nuanced configuration of said databases.

# Proposed Solution
Replace the current method by allowing users to pass in a `map[string]larry.database` that maps the table name to a pre-constructed Larry compliant database.

Locate the MultiDB entry point and the current map[string]string initialization path, then read the larry.database interface used by the package. Done means MultiDB accepts a map[string]larry.database mapping table names to pre-constructed databases, while preserving the intended per-table setup.

Written by the indexing model from the issue text.