Various ROM projections for steady NS toy model

[dreamer2368]

sketches/ns_rom supports various ROM basis and projection:

• RomMode::TENSOR: u/p unified basis
• RomMode::TENSOR2: u/p separate basis
• RomMode::TENSOR3: u-only basis
• RomMode::TENSOR4: u/p separate basis with supremizer enrichment
• RomMode::TENSOR5: u/p separate basis with supremizer projection

Minor changes in SteadyNSSolver:

• Sample generation process collects another sample if a sample fails to converge.
• CGOptimizer class of optimization solver.
• SteadyNSSolver::SolveROM supports restart from a FOM solution.