Migrate G4VECGEOM and G4ADEPT branches to VecGeom 2.1.0

[civanch]

A new version of VecGeom 2.1.0 is available: https://gitlab.cern.ch/VecGeom/VecGeom/-/tree/v2.1.0?ref_type=tags

This includes bugfixes and performance improvements of the library.

Would it be possible to include this new version for G4VECGEOM and G4ADEPT branches for testing?

[cmsbuild]

cms-bot internal usage

[cmsbuild]

A new Issue was created by @civanch.

@Dr15Jones, @ftenchini, @makortel, @mandrenguyen, @sextonkennedy, @smuzaffar can you please review it and eventually sign/assign? Thanks.

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[smuzaffar]

@civanch , I am already testing it via #10711 to get it in default IBs 20.1.X but sure we can first get it in special G4 IBs

[civanch]

@smuzaffar , This is fine that it is in the master. The next G4VECGEOM and G4ADEPT branches will peak up it automatically?

[civanch]

Thanks.