* Update kamon and kanela-agent
Previous version was not compatible with JDK21, see https://github.com/kamon-io/kanela/issues/150.
* Add and configure maven wrapper to use maven 3.9.9
This will make it easier to control which version of maven is used to build eclair, which in turns makes deterministic builds easier, as well as using recent compiler options (to target newer JDKs for example).
For example, even recent versions of Github runner images use an old version of maven and there is no easy way to upgrade.
* Update Dockerfile
We now use multiarch (amd64/arm64) base images.
* Run CI tests with JDK21
* Update doc to recommend Adoptium OpenJDK21
* Target Java 21
Eclair now targets Java 21 and will require a compatible Java Runtime Environment.
It will no longer work on JRE 11 and JRE 17.
This version of logback fixes the following CVE:
"a potential denial of service attack on a centralized logback receiver
when a third party controlling a remote appender connects to said
receiver and could shut down or slow down logging of events."
Eclair isn't affected since we don't use logback receivers, but if there
are applications or plugins that depend on eclair and use logback
receivers, it's better to use the logback version containing the fix.
* Update code dependencies
I also wanted to update logback, but I'm hitting issues because of our
custom logger in `FixtureSpec` (`LoggingEventAware` not found).
* Update build dependencies
We're now using mvn 3.9.2 to build eclair, which reports warnings in some
of the build plugins we use. Updating plugins fixes most of the warnings,
and the remaining warnings have to be fixed by the plugins themselves
to support mvn 4.x.
We now use a regular release zip, and use it in the awseb bundle.
The default logback configuration now logs to a file, like
`eclair-node`, and we use a dedicated logback configuration for AWS
beanstalk.
By default the front reads the node secret key from the node seed in
the standard `.eclair` directory.
