Change binary/source distro names to prefix with apache

[lresende]

What

Apache release policy expects distribution artifacts to carry the full project
name. This renames the binary and source distributions, their dist
subdirectories, and the top-level directory inside each archive to use an
apache-toree prefix.

	before	after
binary package	toree-<VERSION>-bin.tar.gz	apache-toree-<VERSION>-bin.tar.gz
source package	toree-<VERSION>-src.tar.gz	apache-toree-<VERSION>-src.tar.gz
binary archive root	toree-<VERSION>/	apache-toree-<VERSION>/
source archive root	toree-<VERSION>-src/	apache-toree-<VERSION>-src/
dist directories	dist/toree-{bin,src}	dist/apache-toree-{bin,src}

The pip packages already ship under both the toree and apache-toree names
and are unchanged.

Alongside the rename:

• publish-pip uploads both pip packages instead of only the toree one. It
  needs two different container working directories, so the single $(DOCKER)
  invocation is split into two.
• audit now passes dist/apache-toree-pip to verify-release, which it
  previously skipped entirely.
• verify-release matches the new artifact names, and fails when a directory
  contains no artifacts at all. Previously the per-file loop set failure
  only from inside its body, so an empty or non-existent directory produced a
  successful audit that had verified nothing.
• release-build.sh echoes the tag it created and says explicitly when a dry
  run skips the push.

Also updates Scala to 2.12.20 and 2.13.15, and comments out the AddJar system
test — its fixture jar at home.apache.org/~lresende/toree/TestJar.jar now
returns 404. That test should come back once the jar is hosted somewhere
durable.

Testing

CI covers the rename: make clean release builds the renamed bin and src
tarballs on all four Java/Scala combinations.

CI does not run make audit, so verify-release was exercised by hand
against fixture directories, using a throwaway GPG keyring:

case	result
valid artifact, signature and both checksums	exit 0
empty directory	exit 1, ERROR: No release artifacts found
non-existent directory	exit 1 (previously exit 0)
missing or invalid signature / checksum	exit 1
toree-* and apache-toree-* in one directory	both matched
.asc / .md5 / .sha512	excluded from the artifact list
nested subdirectory	not descended into