Add RTA/2023.08.04 stack

This stack is simply a copy of the already deployed DPA/2023.08.04 stack. We need to "name" the stack like this because it is also used for HLT1 in production.

Release checklist (to be filled by the shifter)

• release build validation (to be checked with the MR author)
• RPMs deployment
• CVMFS installation
• web pages update