Create wrapper scripts for the druid database init scripts

### Description

Per @paul-rogers comment in #13713 , suggest creating a script to wrap the database initialization scripts to migrate from Derby to Postgres or MySQL

For example: `bin/init-metadata`

### Motivation

The scripts in `docs/operations/metadata-migration.md` are now mature enough that we don't really need to force the user to check that they copy/pasted this command correctly, and filled in the blanks.

Start by reading docs/operations/metadata-migration.md and reviewing the existing database initialization scripts it documents. Use the proposed bin/init-metadata entry point as the scope, and consider the work complete when the wrapper covers the documented migration from Derby to PostgreSQL or MySQL without requiring users to copy and fill in the commands manually.

Written by the indexing model from the issue text.