fixes for X11 forwarding - fixes for pts and tty (from Oliver)

fixes for X11 forwarding:

1. wrapper around xauth: /usr/local/bin/condor_xauth_wrapper.sh
   wrapper specified in sshd config template: condor_ssh_to_job_sshd_config_template
   (X11 forwarding works by running xauth as a child of the sshd process) \

2. script for the container to source .display from the HOME directory at start: /etc/profile.d/condor_source_display.sh

3. SINGULARITY_HOME = /srv in c4p-htcondor-configs/GridKa-cloud

fixes for pts and tty:

script 10-fixup_singularity.sh from Oliver.

The script deals with a Singularity/Apptainer issue related to pty allocation.
It also adjusts the TERM and locale environment variables.
I let it unchanged.