This change updates the build configuration for Gradle to make use of
its Java Toolchains feature which enables running/testing multiple Java
versions at the same time. This feature can also provision a Java
installation if it is not available on the user's system.

This change updates the Gradle configuration to target Java 17 (instead
of Java 11) as the lowest denominator when running/building OpenDC. This
version of Java has been available for more than a year and is the
latest LTS release.

This change moves build dependencies used by Gradle into the version catalog
to ensure a single location for all dependency versions.

This change updates the Gradle configuration to target Java 11 (instead
of Java 8) as the lowest denominator when building OpenDC. Since the
project has not yet been adopted by (many) other applications, we should
not restrict the project to such an old Java version.

This change adds a workaround to the build configuration so that we can
access the version catalog from pre-compiled scripts in buildSrc. In
this way, we can use the version catalog everywhere.

This workaround is necessary until
https://github.com/gradle/gradle/issues/15383 is fixed.