update Starlight to r300 following the changes in SVN

See merge request atlas/athena!24756

# Conflicts:
#   Projects/AthGeneration/externals/Starlight.cmake

add Gen_tf_txt.py and skel.GENtoTXT.py to allow for LHE-only production in the new production system

21.6 transf

See merge request atlas/athena!24718

add first version of LHEonly.py common fragment to produce 1 Pythia8 even in case of LHE only production,
and skeleton for LHE only production

fix synatax problem in this test

See merge request atlas/athena!24712

add ART test for MG NLO and correct the Epos test using Mc15JobOptions

See merge request atlas/athena!24671

MadGraphControl fix for path patch

See merge request atlas/athena!24666

We do some gaming of MG5_aMC configuration paths during the job running
in order to make sure we don't have afs dependence sneaking in anywhere
(to ensure dependencies are on cvmfs). This patch ensures that if we try
to do that, we don't accidentally cause a crash in the case either that
one of the dependencies is installed locally (not in the release) or in
the case that they line is commented out in the MG5 configuration.

Fixing several typos in MGC

See merge request atlas/athena!24633

This was meant to be a more clever way to check for the appropriate run
directory, both including extra process directories and cleaning up
error messages. There were a bunch of typos in it. It seems to be
working now.

fix synatax problem in MadGraphControl

See merge request atlas/athena!24578

# Conflicts:
#   Projects/AthGeneration/externals/Crmc.cmake

change GENERATOR_VERSION -> GENERATOR_LCGVERSION

fix syntax problem in MadGraphControl/python/MadGraphUtils.py

See merge request atlas/athena!24521

add commons for JetFilter

update to atlasexternals-01-00-51

See merge request atlas/athena!24462

# Conflicts:
#   Projects/AthGeneration/version.txt

update to Lhapdf6.2.3 and versions of generators recompiled with this version of Lhapdf

Add all-pass test filter to give failing events zero weight

See merge request atlas/athena!24333

add MultiBJetFilter - ATLMCPROD-7217

See merge request atlas/athena!24297

update atlasexternalas 1.50

See merge request atlas/athena!24143