Add 'AspectJ_JDK_Update' hint in various places

Add 'AspectJ_JDK_Update' hint in various places

The hint is meant to help AspectJ developers identify the places where
there are to-dos for releases supporting new Java versions. This is work
in progress, new tags can be added wherever necessary in the future. But
for now, the most important places should be covered:

 - AJC version string
 - Test infrastructure (test suites, classes and XML files)
 - BCEL class file version MAJOR_*, MINOR_* constants
 - AjcTask constants for compiler source, target, release
 - LangUtil::is*VMOrGreater methods
 - ASM and JDT Core dependency versions
 - CI workflow file
 - Release notes

The to-do to check the tagged places is also mentioned in RELEASE.md.

Signed-off-by: Alexander Kriegisch <Alexander@Kriegisch.name>