Create a `LicenseDataProvider` plugin API

[sschuberth]

For context, see e.g. #9523 and eclipse-apoapsis/ort-server#1654.

Such providers should provide more than just license text, like currently done via a collection of "loose" functions, but also provide further metadata like URL, alias names etc.

The data model of the ScanCode LicenseDB could serve as an inspiration.

[sschuberth]

The data model of the ScanCode LicenseDB could serve as an inspiration.

We already have some code for that over at the ort-config repository.