Add "application_name" to connections made by go-sqlcmd

[stuartpa]

To enable troubleshooting scenarios when connecting to the server with go-sqlcmd, ensure application_name is populated. (ODBC sqlcmd populates application_named with SQLCMD)

[blzzua]

Is it possible to make this field fill in not with the default value sqlcmd, but with the value from the cli parameter, env variable?