Check vector concepts for all of our solvers.

[bangerth]

#15637 creates a concept for what constitutes a vector-space-vector. We should annotate all of our solver classes with this requirement.

The files in question are specifically these:

> egrep -l -r 'class Solver' include/deal.II/lac/
include/deal.II/lac/solver_selector.h
include/deal.II/lac/solver_minres.h
include/deal.II/lac/solver_qmrs.h
include/deal.II/lac/trilinos_sparse_matrix.h
include/deal.II/lac/solver_idr.h
include/deal.II/lac/petsc_solver.h
include/deal.II/lac/solver_bicgstab.h
include/deal.II/lac/solver_richardson.h
include/deal.II/lac/solver_gmres.h
include/deal.II/lac/ginkgo_solver.h
include/deal.II/lac/slepc_spectral_transformation.h
include/deal.II/lac/trilinos_precondition.h
include/deal.II/lac/solver_relaxation.h
include/deal.II/lac/solver_control.h
include/deal.II/lac/solver_cg.h
include/deal.II/lac/solver.h
include/deal.II/lac/cuda_solver_direct.h
include/deal.II/lac/trilinos_solver.h
include/deal.II/lac/slepc_solver.h
include/deal.II/lac/solver_fire.h

[bangerth]

This would also address at least a part of what we had intended with the VectorSpaceVector class (see #3073).

[bangerth]

#16995 adds vector space concepts for the VectorType template argument of solvers. I did not yet add constraints on the MatrixType and PreconditionerType template arguments yet, but that is next.