Stop publishing for Scala 2.13.0 to 2.13.8

[jackkoenig]

Older versions of Scala do not work with newer versions of the JVM, but Scala 3.8 requires Java 17+. In the interest of simplicity, this PR drops Scala <= 2.13.8. We could make this work by splitting the build but I don't think that effort is worth it unless we have a very compelling reason.

I'm also inclined to just do this on a minor version of our own (I doubt anyone is still on that old of Scala and they should be able to bump easily) unless we want to hard break main towards Chisel 8.

Contributor Checklist

• Did you add Scaladoc to every public function/method?
• Did you add at least one test demonstrating the PR?
• Did you delete any extraneous printlns/debugging code?
• Did you specify the type of improvement?
• Did you add appropriate documentation in docs/src?
• Did you request a desired merge strategy?
• Did you add text to be included in the Release Notes for this change?

Type of Improvement

• API modification

Desired Merge Strategy

• Squash

Release Notes

Users of older Scala minor versions are always advised to upgrade to the newest minor version within their major version.
If this is a problem for any users, please reach out to us on Github.

Reviewer Checklist (only modified by reviewer)

• Did you add the appropriate labels? (Select the most appropriate one based on the "Type of Improvement")
• Did you mark the proper milestone (Bug fix: 3.6.x, 5.x, or 6.x depending on impact, API modification or big change: 7.0)?
• Did you review?
• Did you check whether all relevant Contributor checkboxes have been checked?
• Did you do one of the following when ready to merge:
  • Squash: You/ the contributor Enable auto-merge (squash) and clean up the commit message.
  • Merge: Ensure that contributor has cleaned up their commit history, then merge with Create a merge commit.

[jackkoenig]

I'm going to just debump Mill for now and put this on the Chisel 8 Tracker.

[seldridge]

FWIW, I'm good with dropping support for < 2.13.9. I'm not sure who would truly object to this?

[jackkoenig]

FWIW, I'm good with dropping support for < 2.13.9. I'm not sure who would truly object to this?

Probably no one, but it's pretty easy to revert my Mill bump from last week and then just do this as soon as we decide to start Chisel 8 work on main, even if that's literally tomorrow it's all easy enough.