Implemented new kernel interface for compositional properties

[francoishamon]

This PR implements a simple kernel interface for the compositional property updates:

• Component fractions
• Phase volume fractions
• Phase mobilities (FV and mimetic)
• Total mass densities (wells)

with a base class that contains the various launch functions, and derived classes implementing the compute functions. The goal is to make the extension to thermal easier using callbacks in the compute functions. The non-local terms (fluxes, etc) will be done in #1696, and the well kernels in another PR.

The downside is that I am no longer able to use explicit instantiation with this approach.

The PR is ready for ready for review, and passes the integrated tests on Quartz and Lassen (no rebaseline necessary).

[klevzoff]

LGTM!

[mkhait]

"The downside is that I am no longer able to use explicit instantiation with this approach"

@francoishamon, why is that downside? I always thought its a benefit )

[francoishamon]

@mkhait Previously, in the compositional solver, we were explicitly instantiating the templated functions (mainly the launch functions) in the cpp files to speed up compilation (particularly for the GPU builds that take forever). But now, with the new kernel classes, it has become harder to do and I removed many of these explicit template instantiations.

I don't know enough about compilation to provide a more detailed answer :) and experts will jump in to add details. The long term approach that we want to follow is to use just-in-time compilation to speed up our builds, as in this PR.