svd not supported for lower bidiagonal matrices

[andreasnoack]

As reported in JuliaLinearAlgebra/TSVD.jl#33 and fixed by #156. However, I think this should be done with a pass of Givens rotations to flip the Bidiagonal. Currently, the error is

julia> GenericLinearAlgebra._svd!(Bidiagonal(randn(4), randn(3), :L))
ERROR: SVD for lower triangular bidiagonal matrices isn't implemented yet.
Stacktrace:
 [1] error(s::String)
   @ Base ./error.jl:35
 [2] __svd!(B::Bidiagonal{Float64, Vector{Float64}}, U::Matrix{Float64}, Vᴴ::Matrix{Float64}; tol::Float64)
   @ GenericLinearAlgebra ~/.julia/dev/GenericLinearAlgebra/src/svd.jl:252
 [3] __svd!
   @ ~/.julia/dev/GenericLinearAlgebra/src/svd.jl:156 [inlined]
 [4] #_svd!#40
   @ ~/.julia/dev/GenericLinearAlgebra/src/svd.jl:292 [inlined]
 [5] _svd!(B::Bidiagonal{Float64, Vector{Float64}})
   @ GenericLinearAlgebra ~/.julia/dev/GenericLinearAlgebra/src/svd.jl:286
 [6] top-level scope
   @ REPL[17]:1