Draft: SVD: remove deprecated code, fix -Wmaybe-uninitialized

Reference issue

What does this implement/fix?

Deleted all the deprecated code in JacobiSVD and BDCSVD. The Wmaybe-uninitialized warning in GCC is fixed by replacing an assignment with a placement new.

TODO: we should static assert in matrixU()/matrixV() instead of runtime assert since this should be known at compile time. This breaks a ton of code as we have a gazillion runtime branches to handle the various unitary calculations. The side effect of implementing this would be to eliminate a bunch of unused code if the user is only interested in calculating the singular values or one unitary.

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