Add a basic controller

[stano45]

Added a basic python controller to:

• Program switch 1 (same initial match-action tables as previously in s1-runtime.json)
• Expose three http endpoints: /insert_hop, /update_hop and /delete_hop to insert, update and delete entries from the ecmp_nhop table (this is an incomplete implementation for experimenting, and will be changed soon, e.g.to update the send_frame egress table)

Other additions:

• Patched utils/Makefile using https://github.com/p4lang/tutorials/blob/9e00b35ceb3ed276aeb975299ac1975e19aad93f/vm-ubuntu-24.04/patches/tutorials-support-venv.patch#L10 to make this work on the Ubuntu24 VM from the tutorial repo
• Updated utils/p4runtime_lib/switch.py to also support table entry deletion
• Dumped all python dependencies to requirements.txt - of course this is not sufficient to run everything from scratch, since the pre-built VMs from the tutorial repo do a lot of heavy lifting to build the environment, but it's a start
• Added a Makefile in the root of the project, to more easily run the load balancer and controller (in 2 terminals using make load_balancer and make controller)
• Formatted json files, same way as in Format all json files p4lang/tutorials#617