prosody: extend test.sh past the version string grep

prosody: extend test.sh past the version string grep

The previous test only grepped prosody.version and ran `prosodyctl
about`, which still passes when the parts that actually differ per
target architecture are broken.

Drive the rest of the package instead:

- Assert `prosodyctl about` reports Lua 5.4. The wrapper silently falls
  back to /usr/bin/lua (5.1 on OpenWrt) if --runwith is lost, and
  prosody 13 refuses to run on it.
- Require loader.lua to be installed, since prosody(ctl) cannot resolve
  any of its 'prosody.*' requires without it.
- Register and unregister an account on the sample VirtualHost. That is
  the only path exercising util.datamanager storage together with the
  internal_hashed SCRAM derivation, and it must not leave the cleartext
  password on disk.
- Load each of the 13 compiled util/*.so extensions through their
  luaopen_prosody_util_* entry points.
- Check known-answer vectors through util.hashes and an Ed25519
  sign/verify round trip through util.crypto (both linked against
  libopenssl), IDNA plus stringprep through util.encodings (libidn),
  and XML parsing through util.xml (luaexpat).
- Require lfs, socket and ssl, so a missing luafilesystem5.4 /
  luasocket5.4 / luasec5.4 runtime dependency fails here rather than on
  a user's router.

The XMPP daemon is still never started: it would block forever under
QEMU emulation.

Signed-off-by: Alexandru Ardelean <redacted>