Prepare and distribute spark plugin runtime artifact

[jbonofre]

For Polaris 1.0, we plan to distribute spark plugin runtime artifact.
This jar file shades dependencies (iceberg, ...).
As any distribution artifacts, this artifact should include LICENSE, and NOTICE, (and optionally DISCLAIMER).
So, we have to:

1. Include spark plugin runtime artifact in gradle (to publish on Maven)
2. Include correct LICENSE, and NOTICE in the jar file

[adutra]

FYI I'm a little worried about the current distribution layout of the so-called "Spark plugin" and the inclusion of the entire Spark Iceberg runtime jar:

#1857 (comment)

[snazy]

I second both of your two major concerns.

[flyrain]

1 was fixed by #1830.
2 was fixed by #1834 and #1839

Close this as two issues have been fixed.

[jbonofre]

👍 thanks everyone for this great work !