Improve Add Database Connection dialog for SQLite, DuckDB, BigQuery, and Snowflake

[eirikbakke]

The "Add Database Connection" dialog supports various kinds of database-specific connection fields (host, port, database name etc.) These are automatically substituted into the JDBC driver specific JDBC URL.

This PR adds support for a "File" field, which will be shown if the user is using the JDBC drivers for SQLite or DuckDB. There is a "Browse" button that can be used to pick the file from a file browser. Furthermore, the username and password fields are hidden for these drivers, which are known not to require this kind of authentication.

For SQLite and DuckDB, there's a warning if the selected file is not of the right kind. (Useful because SQLite files do not have any kind of standardized file extension.)

For comparison, this is what the Add Database Connection dialog looked like before, for SQLite:

(There are some proprietary JDBC drivers for SQLite that do allow a password to be used for encryption, but in this rare case the user could use a connection property to pass this information instead.)

[eirikbakke]

The NewConnectionPanel uses the NetBeans Matisse Form Builder, by the way. The way it works is that the form contains every possible field available, and then individual fields are shown or hidden depending on what fields are used in the JDBC URL template string.

Here is the full dialog as it appears in the form builder:

To insert the "File" field I ended up hand-editing the ".form" file, reloading it in the form builder, making some adjustments, and then saving it again together with freshly generated initComponents() code. So the final "form" file committed here is generated by Matisse, not hand-edited by me.

[eirikbakke]

I added another commit which recognizes Snowflake JDBC URLs, just since we're already making enhancements to this piece of code.

[eirikbakke]

I squashed the previous review edits, and also added a separate commit which recognizes Google BigQuery JDBC URLs.