Add "database" to sqlconfig file (useful for creating contexts to specific user DBs in Azure SQL)

[stuartpa]

Enabled endpoints to be created with default database set, useful for Azure SQL connections. (the local container instances created with sqlcmd create set the default database on the login, so database not needed in the sqlconfig file)

[noraj]

TL;DR:

• ☑️ sqlcmd query
• ☑️ sqlcmd config connection-strings
• ❌ ~/.sqlcmd/sqlconfig
• ❌ sqlcmd config add-context or sqlcmd config add-endpoint

sqlcmd config add-endpoint and sqlcmd config add-context does not allow to configure a database so by default all CLI commands or interpreter are always using master. ~/.sqlcmd/sqlconfig does not seem to support a database option either. However, it is supported for the query command (see #287, #288, #242), the config connection-strings sub-command (see #277, #280).