feat: Use stability test in flash

[dkachuma]

This PR adds a stability test before launching the negative two-phase flash. If the mixture is not found to be unstable for the test compositions during the stability test, it is simply labelled as liquid or vapour using the Li-correlation as described in the documentation. Only when the mixture is found to be unstable, is the negative two-phase flash launched.

• The Li-correlation requires the critical volumes. This makes the critical volume an input for all the two-phase compositional models (not just the ones that use LBC viscosity).
• The stability test is changed. Once a test composition is found that makes the TPD negative, the iterations are terminated even before reaching the stationary point.
• A description of the flash procedure is added to the CompositionalMultiphaseFluid rst.
• Some heuristics for single phase detection are removed from the flash.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 99.06542% with 2 lines in your changes missing coverage. Please review.

Project coverage is 56.36%. Comparing base (f6caac7) to head (10a55cd). Report is 1 commits behind head on develop.

Files	Patch %	Lines
...ompositional/models/NegativeTwoPhaseFlashModel.hpp	95.45%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #3206 +/- ## =========================================== + Coverage 56.01% 56.36% +0.34% =========================================== Files 1053 1056 +3 Lines 89115 89233 +118 =========================================== + Hits 49919 50294 +375 + Misses 39196 38939 -257 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[paveltomin]

review?