Expose Firebird 5.0 isc_dpb_parallel_workers as a property in DatabaseConnectionProperties

[mrotteveel]

Currently, isc_dpb_parallel_workers can be set through the JDBC URL, but requires using setProperty(String, String) or setNonStandardProperty(String) to set it on - for example - DataSource implementations. Exposing it as Java property (getter/setter) on DatabaseConnectionProperties would be helpful.

When doing this, also add additional alias matching Java property name, and "promote" to supported properties (moving it from section Formally unsupported properties in StandardConnectionPropertyDefiner to section Database properties).

[mrotteveel]

NOTE: #739 and #740 may make it sensible to add the option to AttachmentProperties instead of DatabaseConnectionProperties, but that should be decided when implementing those features.