Reactivate Downgrade tests on 1 and pre

[fhagemann]

This PR reactivate Downgrade tests on 1 and pre, while excluding the downgrade packages that are not compatible with 1 and pre (namely FillArrays, StaticArrays and Distributions, see #419 for details).

[fhagemann]

For reference, the original comment posted in #419 (comment):

Here are some changes to the lower package compats required to work on julia-1.11:

• The type parameter in AbstractTriangular was removed in julia-1.11.
  • AbstractTriangular was explicitly called in FillArrays before 0.13.8. Thus, the compat in the General registry was manually adjusted to disallow the use of FillArrays pre-0.13 with julia-1.11.
    ==> I adjusted the lower compat of FillArrays to 0.13.8.
    ==> I adjusted the lower compat of Distributions to 0.25.49 to allow for [email protected].
  • AbstractTriangular was also explicitly called in StaticArrays before 1.5.17. Thus, the compat in the General registry was manually adjusted to disallow the use of StaticArrays pre-1.5 with julia-1.11
    ==> I adjusted the lower compat of StaticArrays to 1.5.17.

In addition, the impossibility of running Geant4 tests on x86 causes the tests that were previously passing to fail. Therefore, I explicitly removed Geant4 from test/Project.toml in the x86 test.

[fhagemann]

Looks like Unitful does not compile on julia-1.12 if the version is below 1.12.3 due to some definition of Angström.
JuliaPhysics/Unitful.jl@559bd09
I excluded downgrading Unitful for now on pre as well to prevent the tests from failing here.