Expand scope of sqlcmd config file to other client tools and drivers

As the adoption of this modern CLI increases, the config file generated by sqlcmd would be present everywhere the go-sqlcmd is used.
The config file has all the information needed to establish a connection.
It is further associated with a context name.
Theoretically, any client driver or tool which has access to this config file should be able to establish a connection to the server by just accepting the context name from user application.

This issue is created to expand the scope of sqlcmd config file to contain other connection properties as well which the other tools and drivers can consume internally given a context name.

This also provides us with an opportunity to come up with common connection properties or a common format which all other drivers and tools can then uniformly consume and users don't have to deal with driver or tool specific connection string format.

Start by locating the sqlcmd config file handling and the code that resolves a context name into connection information. Review which connection properties are currently stored and how other client tools or drivers could consume them. Done means defining and implementing a common set of properties or format that supports establishing connections from a context name.