Update some boundaries and initializers for mixtures

[tulioricci]

• modifies some eos functions to not need a full cv, so we can use them for initialization (#955)
• deprecate MixtureInitializer and use Uniform instead to avoid duplicate codes.
  • updated the existing tests
• rename some arguments of initializers to keep consistent nomenclature along the different functions
• update BCs:
  • to handle mixture
  • use MengaldoBC as the inherited class (#576)
  • make DummyBoundary inherit FluidBoundary instead of PrescribedBnd; added test
• examples:
  • replace poiseuille-local-dt with blasius flat plate flow, which exercise more BCs
  • include pulse-mixture to exercise mixture BCs

Questions for the review:

• [x] Is the scope and purpose of the PR clear?
  • [x] The PR should have a description.
  • [x] The PR should have a guide if needed (e.g., an ordering).
• [x] Is every top-level method and class documented? Are things that should be documented actually so?
• [x] Is the interface understandable? (I.e. can someone figure out what stuff does?) Is it well-defined?
• [x] Does the implementation do what the docstring claims?
• [x] Is everything that is implemented covered by tests?
• [x] Do you see any immediate risks or performance disadvantages with the design? Example: what do interface normals attach to?