Proposing to move JMC 9 to JDK 17.

[Marcus Hirt]

Hi all,

I propose that we move JMC 9 to use JDK 17 for compiling all parts of
JMC 9, including JMC core. The reason is that we need to move to Tycho
3.0 to properly support working with the project in the newer versions
of Eclipse.

I also propose to require JDK 17 for running all parts of JMC 9, to
simplify requirements, and to allow developers to use JDK 17 features
when developing JMC. We already require JDK 17 to run the RCP
application build of JMC, since newer versions of the Eclipse platform
require JDK 17 to run.

Note that it will still be possible to connect to, read and process
JFR recordings from, and run the other tools  (e.g. JOverflow) on
processes running JDK 8+.

Kind regards,
Marcus