NOTICE requirements of dependencies with overly verbose NOTICE files

We're working on cleaning up our L&N over at HADOOP-12893. One question that came up is what we should add to our NOTICE for dependencies that have overly verbose NOTICE files.

For example, this is the Jetty NOTICE file:

https://github.com/eclipse/jetty.project/blob/jetty-9.3.x/NOTICE.txt

It lists out its dependencies and licenses, but that's not what NOTICE is for. We also already have LICENSE and NOTICE entries for all of these transitive dependencies.

This is the Xerces NOTICE:

https://svn.apache.org/repos/asf/xerces/java/trunk/NOTICE

We're also an Apache project, so it seems like the ASF lines are unnecessary. The copyright attributions also seem potentially unnecessary, considering this code was donated to the ASF when it became an ASF project.

Finally, here is the snappy-java NOTICE:

https://github.com/xerial/snappy-java/blob/master/NOTICE

These don't look like legally required notices either. 3-clause BSD doesn't require a NOTICE IIUC, we don't need to NOTICE our own code from Hadoop, and listing contributors isn't what NOTICE is for either. Not sure about the statically linked libstdc++, but LEGAL-230 did clear snappy-java for ASF use.