Update to Java 17

[ronreynolds]

No description provided.

[ronreynolds]

converted this to an issue so i can add comments (apparently that's not possible until it's made an issue).
per standup i really think we should only upgrade the JDK version with great care and intention since we're telling our SDK customers that they MUST use this version or better in order to use the SDK jar. Java-11 seems reasonable (tho many projects are still stuck in Java-8) but Java-17 seems excessive to me.

[ronreynolds]

also found this regarding team communication best practices on github - https://docs.github.com/en/discussions/guides/best-practices-for-community-conversations-on-github
haven't read it all yet.

[ronreynolds]

another MR updates the BUILD to work with Java-21's javac but the CODE is still Java-11 compliant and the build is still generating Java-11 bytecodes, which i think is crucial if we don't want to upset users by forcing them to upgrade to a newer JVM without a very good set of reasons.