Fix NPE in revapi-java and Java 17 compatibility
The new version of
revapi-java, 0.25.0, contains an important fix that caused a `NullPointerException`in the package matcher which would occur when it encountered a missing class. This should fix issues #244 and #249.
The build and dependecies were updated to be compatible with Java 17 and the testsuite is now successfully passing on it.