Rework cookbooks and benchmarks with internal constraints using the prescribed solution plugin system

[gassmoeller]

We have some cookbooks (and also tests) that use the signal mechanism to add internal constraints on the solution. These can be rewritten to use the prescribed solution plugin system introduced in #6660.

I noticed:

• cookbooks/prescribed_velocity
• cookbooks/prescribed_velocity_ascii_data

But possibly there are more.

@lhy11009 mentioned he would work on some of these, but I think anyone with interest in the new system is welcome to convert some tests or the cookbooks.