Remove dependency on PVT package

[dkachuma]

This PR removes the dependency of GEOS on the external PVTPackage in favour of local, "native" implementations for compositional multiphase fluids.

As part of this transition, the CompositionalMultiphaseFluid constitutive model (which acted as a wrapper around the PVT package) has been entirely removed and replaced by the native CompositionalTwoPhaseFluid model across all integration tests and input files.

Additionally, this refactor simplifies the execution policies across all fluid models. Since native models inherently support device execution, individual exec_policy type definitions have been removed from the fluid classes, and the solvers have been updated to directly utilize parallelDevicePolicy<>.

Key Changes

• Removed PVT Package Dependency: Removed the ENABLE_PVTPackage CMake option and stripped out all associated build logic.
• Deleted Wrapper Code: Deleted CompositionalMultiphaseFluidPVTPackage.hpp/cpp and its wrapper code. (Note: The git submodule for PVTPackage is not yet removed from the repository in this PR.)
• Fluid Model Replacement:
  • Replaced CompositionalMultiphaseFluid with CompositionalTwoPhaseFluid in all XML input files, integration tests, and schemas.
  • Updated equationsOfState string identifiers in input files (e.g., PR -> PengRobinson, SRK -> SoaveRedlichKwong).
• Updated the Sphinx documentation and XML schema (schema.xsd) to reflect the removal of CompositionalMultiphaseFluid and the PVT package.
• Updated all affected integration tests (fluidFlowTests, wellsTests, constitutiveDriver) to use the new native CompositionalTwoPhaseFluid model.
• Verified that analytical derivatives and multi-phase flow behaviors remain correct under the native implementation.

[rrsettgast]

@dkachuma

So are we no longer going to be able to run a 3-phase problem?

[dkachuma]

@dkachuma So are we no longer going to be able to run a 3-phase problem?

@rrsettgast We were never able to run 3-phase models with the PVT package (see for example #3257). I did implement the 3-phase model with the "immiscible water flash" (testPVT_ThreePhaseCompositional.xml:38-56).

[jhuang2601]

The file CompositionalMultiphaseFluid.rst should be renamed to CompositionalTwoPhaseFluid.rst for better clarity.

[rrsettgast]

@dkachuma Does this PR represent zero capability loss, even if that capability wasn't good?

[dkachuma]

@dkachuma Does this PR represent zero capability loss, even if that capability wasn't good?

@rrsettgast The two-phase model that I added covers the compositional model that was provided by the pvt package. So I'd say no loss of capability.

[tjb-ltk]

@dkachuma So are we no longer going to be able to run a 3-phase problem?

@rrsettgast We were never able to run 3-phase models with the PVT package (see for example #3257). I did implement the 3-phase model with the "immiscible water flash" (testPVT_ThreePhaseCompositional.xml:38-56).

@dkachuma When you say 3 phase is not supported...the doc shows description for live black oil... which is also immiscible

[dkachuma]

@dkachuma When you say 3 phase is not supported...the doc shows description for live black oil... which is also immiscible

Three-phase black oil works. But this is "natively" implemented in geos and doesn't depend on the PVT package. What I meant to say is that the supposed compositional 3-phase model via the pvt package wasn't actually implemented and therefore doesn't work.