Add new and pre-release Java builds

[bowbahdoe]

• Adds a newer stable version of Java than 15 w/ 20
• Adds some early access builds as well

The reason I want 21-ea specifically is so that I can have my book run code snippets using anonymains
https://openjdk.org/jeps/445

[bowbahdoe]

Also, huge apologies if they don't build. I see the other github issue where the person didn't build them locally and that was bad, but I have an M1 mac so the docker images actually don't work on my machine. I would likely have to use the workflow here to validate unfortunately :(

[bowbahdoe]

Good news! got a linux laptop to test all of this and they did build with some changes

Bad news! The entire reason i want to have these ea builds is moot since the change hasnt been merged in yet. Kindof a bummer, but it will come out eventually and the central question of "would the piston folks be okay adding pre-release java builds to the public api/built in set" is still worth figuring out/for me

[HexF]

Not sure how semver compliant this version number is

[bowbahdoe]

I ended up giving up waiting for this and forked the rust playground to do what I wanted. https://java-playground.com

I'll leave the issue up in case anyone else is still interested, but i've moved on.