[FCC] Centralize common detector components

[BrieucF]

I open this issue to discuss the possibility to have the compact files of components that are common to all FCC detectors (essentially MDI) in a central place. This will ensure consistency across FCC detectors and will ease developments/maintenance. Currently things have to be fixed/updated in several places.

The place could be FCCee/MDI/compact/.

And what should go there is:

• BeamPipe
• Beam instrumentation
• HOM Absorbers
• LumiCal
• Magnetic fields of compensating solenoid and FFQuad
• Material needed for all the above
• Dimensions needed for all the above

Thoughts, comments?

[tmadlener]

I would like to add one additional user that does not live under FCCee that would also like to profit from this: ILD_l5_v11 and ILD_l5_v09. If it's easily possible to do this in a way where we could also simply include the bits there without having to copy (and maintain them), I think this should be done. I would be happy to help in testing for that.

[danieljeans]

strong support from me! for same reason as @tmadlener

[aciarma]

I opened a PR #344 for this issue