DDSim,Meta: Fix formatting for dict

The ddsim --meta.runNumberOffset command-line argument doesn't work
correctly (and similarly for event number).

On a machine running

```
LSB Version:    :core-4.1-amd64:core-4.1-ia32:core-4.1-noarch
Distributor ID: Scientific
Description:    Scientific Linux release 7.3 (Nitrogen)
Release:        7.3
Codename:       Nitrogen
```

I do

```
. /cvmfs/sw.hsf.org/key4hep/setup.sh
```

The then command

```
ddsim  --compactFile $LCGEO/FCCee/compact/FCCee_o1_v05/FCCee_o1_v05.xml -G -N10 --outputFile out.edm4hep.root --meta.runNumberOffset 735001  2>&1|tee log
```

eventually crashes with the error

```
Geant4UI         INFO  +++ EventAction> Install Geant4 control directory:/ddg4/EventAction/
Traceback (most recent call last):
  File "/cvmfs/sw.hsf.org/spackages7/dd4hep/1.23/x86_64-centos7-gcc11.2.0-opt/q4qtg/bin/ddsim", line 25, in <module>
    RUNNER.run()
  File "/cvmfs/sw.hsf.org/spackages7/dd4hep/1.23/x86_64-centos7-gcc11.2.0-opt/q4qtg/lib/python3.10/site-packages/DDSim/DD4hepSimulation.py", line 368, in run
    e4Out.RunNumberOffset = self.meta.runNumberOffset if self.meta.runNumberOffset > 0 else 0
TypeError: '>' not supported between instances of 'str' and 'int'
 *** Break *** segmentation violation
```

The arguments are never converted from strings to integers.
The change here fixes this.

This adds the arguments `--gun.etaMin` and `--gun.etaMax`. If both
`thetaMin` and `etaMax` are specified, `etaMax has precedence.

This makes sure a correct URI is passed to the documenthandler (XMLLoader)

Co-authored-by: Andre Sailer <andre.philippe.sailer@cern.ch>

This enables ddsim to accept `--inputFiles example.hepmc3.tree.root` files as produced by the [HepMC3 rootIO writers](https://gitlab.cern.ch/hepmc/HepMC3/-/tree/master/rootIO/include/HepMC3).

There are two rootIO writers: `WriterRoot` writes HepMC3 objects to a ROOT file, while `WriterRootTree` writes a ROOT TTree with events. There are two corresponding rootIO readers. When HepMC3's `deduce_reader` is passed a `.root` file, it only [attempts to use](https://gitlab.cern.ch/hepmc/HepMC3/-/blob/master/include/HepMC3/ReaderFactory.h#L107) the `WriterRootTree`.

Since `.root` is a bit too generic as an extension (it does not indicate the data model) and since ddsim already uses multiple extensions in output formates, e.g. `.edm4hep.root`, I considered that the intent is best conveyed with `.hepmc3.tree.root` (making it clear that the HepMC3 data model is used, stored in TTrees, inside the ROOT file format).

With this change it is now also possible to run ddsim against remote HepMC3 events on an xrootd server, e.g.
```
ddsim --compactFile $DD4hepINSTALL/DDDetectors/compact/SiD.xml -N 10 --inputFiles root://dtn-eic.jlab.org//work/eic2/users/wdconinc/pythia8NCDIS_5x41_minQ2\=1_beamEffects_xAngle\=-0.025_hiDiv_vtxfix_1.hepmc3.tree.root --outputFile output.edm4hep.root
```

Some time in the past, the simple fixed momentum setting for particle gun was lost.

Now we set a fixed energy if the Energy property is set, otherwise we
use momentumMin and momentumMax to chose a momentum from a range.
Also changed some printouts to show the range we chose and the final
value used during simulation.

DDSim: compactFile can only be one instance, otherwise we cannot overwrite what is in the steeringfile, still takes multiple XML files

From https://stackoverflow.com/a/41153081

Needed for python2.7 compatibility

The XML files need to follow the structure where at the end is a closer file.
compactFile takes multiple arguments, or multiple instances of compactFile or both.

  ddsim --compactFile $DD4hep/examples/CLICSiD/compact/SiD_multiple_inputs.xml $DD4hep/examples/CLICSiD/compact/SiD_detectors_1.xml --compactFile $DD4hep/examples/CLICSiD/compact/SiD_detectors_2.xml $DD4hep/examples/CLICSiD/compact/SiD_close.xml --runType shell