Add a Physics for THM compressible Euler flow model

[GiudGiud]

I hope to figure out at least with VACE:

• [x] channels
• [x] inlets/outlets
• [x] simple junctions

with FV

• [x] channels
• [x] inlets/outlets
• [x] simple junctions
• [x] orienting pipes
• [ ] heat
• [ ] scalars

I ll remove the WCNSFV part from the PR and put it into another PR. I m just trying things here to make sure the design will suit our needs

[GiudGiud]

thanks for the early feedback!

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