feat(util/scoped_vec): make scoped_vec template
fixup
refactor(dsolvers): remove icp/ode solvers
refactor(realpaver): remove delta-related code

For the simplicity, I removed them. Later, we can add them back.
fix(util/scoped_env): add insert method, cbegin/cend
feat(dsolvers/nra_solver): implement incremental ICP
checkpoint