Run all the LinearAlgebra tests

[ViralBShah]

Fix for #70

Note that for Julia versions older than 1.7, the system image (with MKL) building fails because the process of overwriting it is unreliable in CI (e.g. on macOS we can't overwrite at all, and linux and windows have other issues). This will not really be a problem since 1.7 will be out soon and so the stable as well as the nightly tests will pass.

We don't expect this package to change a whole lot. The main purpose of these tests is actually for PkgEval.

[KristofferC]

Did you confirm that the linear algebra test here are run with MKL? The tests are run in a new process and I dont see what would load MKL in that process.

[ViralBShah]

Ok. I need to load the MKL package then in the new process. How do I do that? Maybe I should not use Pkg.test().

[KristofferC]

Yes, maybe just

include(joinpath(Sys.STDLIB, "LinearAlgebra", "test", "runtests.jl"))

[ViralBShah]

Trying that in #87