Add MixtureEOS tests and more mechanisms

[tulioricci]

• Mechanisms:

  • Update 7sp UIUC and rename past 7sp mechanism
  • Add mechanism for Y3 prediction
  • Add mechanism for graphite oxidation

• Add MixtureEOS test.

  • If I am blind and these tests are done somewhere else, I will remove test_eos.
  • If indeed they are not done anywhere else, any other suggestions for tests?

Questions for the review:

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

[MTCam]

👍 If we can, we should add the new mechanisms to the existing tests.