VANTAGE coupling

[jwscook]

Impact ionisation, charge exchange and recombination all working with SingleField solver in prototype branch:
https://github.com/ExCALIBUR-NEPTUNE/NESO-Tokamak/tree/Reactions

Also have user specified sources, sinks and initial particle distribution working although not that performant.

Need to add:
Surface sources/sinks/reactions
User specified reaction data
Working with other EquationSystems

We may have some breaking changes in VANTAGE, so hold off starting this (23 April 25)
VANTAGE API changes incorporated (2 May 25)

[jwscook]

Pretty much done, need to check factors of 2/3 etc.
Momentum equation is broken in DG version due to MPI boundary bug...

[jwscook]

"Momentum equation is broken in DG version due to MPI boundary bug..." from above should be in another issue...

Specular reflections from surface reaction capability are now available in NESO-Tokamak. Upstream change to Reactions has been made...

[jwscook]

NESO-Tokamak is up to date with Vantage developments.

[jwscook]

Thermal, specular and absorption (10%) particle boundaries required. absorption cleans neutrals that never leave the boundary / enter the plasma

[jwscook]

Recombination is done. Projection is faster. Need to add surface sources.

[jwscook]

Recombination test is almost done.