Upon special request by Andy Clement, I included 'lib' as a child module
in the parent POM again, making several modules which refer to
downloaded library files dependent the 'lib' module. I am not sure I
caught all of them, but I hope so.

Now after cloning the project and configuring the token for reading from
GitHub Packages (sorry!), you can just run a Maven build for the main
project and no longer need to fail the first build, read the Maven
Enforcer message and run 'cd lib && mvn compile' as a first step. This
convenience comes at the price of a more complex POM and two new
profiles:

  - Profile 'provision-libs' is auto-activated by the absence of a
    marker file, kicking off the library provisioning process and
    creating same marker file at the end, if successful. Therefore,
    during subsequent builds libraries will not be re-provisioned,
    because the marker file exists and Maven skips all download and
    (un)zip steps, which saves build time and bandwidth. Otherwise
    offline builds would not work either.

  - Profile 'clean-libs' needs to be activated manually, because by
    default 'mvn clean' will not erase provisioned libraries. In most
    cases, even after a clean a developer does not want to re-provision
    all libraries if they have not changed (e.g. new JDT Core build).
    But if you do wish too erase the libraries and the marker file, just
    call 'cd lib && mvn -P clean-libs clean'.

Please note: The Maven Enforcer build step, which additionally checks
for existence of other files, still exists and was moved from the parent
POM to 'libs'. No matter if provisioning was just done or skipped
because the main marker file exists, a quick heuristic check for that
list of files is done during each build, failing the build with a
comprehensive message if an inconsistency was found. The error message
says which files are missing and tells the user:

  "There is an inconsistency in module subdirectory 'lib'. Please run
  'mvn --projects lib -P clean-libs clean compile'. This should take
  care of cleaning and freshly downloading all necessary libraries to
  that directory, where some tests expect them to be."

This should cover the topic.

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

If 'name' is identical to 'artifactId' and 'packaging' has the default
value 'jar', we can just remove those tags from the POM.

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

Notably, this change involves a partial revert of @4a5660b3, because we
are not using JUnit Jupiter yet but still JUnit 4 tests. See discussion
under commit at https://github.com/eclipse/org.aspectj/commit/4a5660b3.

Many other warnings - concerning both used undeclared and unused
declared dependencies - were eliminated by adding or removing the
corresponding dependencies from the POMs. Furthermore, I tried to make
sure that some clearly test-scoped dependencies are now actually
declared as such, so as to avoid unwanted transitivity bleeding into
compile scope and maybe unwanted classes ending up in uber JARs via
Maven Shade or Maven Assembly.

TODO: I am not so sure why modules other than 'run-all-unit-tests' would
depend on test JARs. I hope I broke nothing essential there. As of
today, the other modules where I found '<type>test-jar</type>'
dependencies are:
  - ajde
  - testing
  - testing-drivers
  - tests
  - weaver

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

Get rid of system paths. Instead, rely on JDT Core Shadows to deploy
both binary and source JARs to GitHub Packages. The former module
directory was deleted completely. Instead, the JARs are redundantly
copied into 'libs/jdtcore-aj' in order to be found there by tests and
other Ant scripts.

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

Duplicate dependencies, missing or mismatching versions

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

Signed-off-by: Lars Grefer <eclipse@larsgrefer.de>