Upgrade to Spark 3.5.0 or later

[darabos]

I've tried upgrading to 3.4.1 and 3.5.0. In both cases computeZValues fails to compile with a mysterious Breeze error. I tried upgrading to Scala 2.12.18, but that has a conflicting dependency with Play 2.8. Play 2.9 doesn't support Scala 12. I tried upgrading to Scala 2.13. There are lots of simple errors, reported as quickfixable. I guess they would be fixed in VS Code? I tried the Scala Metals extension, which sets up Bloop but just reports an endless stream of errors.

I tried upgrading to Spark 3.3.3, but it's not on Conda Forge. So it's 3.3.2 for us for a while until we sort this out.