ENH: BilgerMixtureFraction: New function object

Summary

A contribution by a community member, @g3.

See #1915 (closed)

Details of new models (If applicable)

See #1915 (comment 49598)

Risks

N/A

WIP issues

• The FO needs info from specieComposition(): see the line
• The function can be called through ThermoType (i.e. thermoPhysicsTypes.H), but there are too many template-template classes thereat. This would create a very long and thus annoyingly redundant piece of repeating code.
• Instead, ReactionThermo could be used. But ReactionThermo does not have access to the info. Even in TDACChemistryModel, specieComposition was fetched through ThermoType.
  • Note that if ReactionThermo is used, some solvers may not run the FO.

Bat-signal: @andy @Sergio