Enforce checks and limits on mass scalars

[psharda]

This PR will:

1.) Ensure we return an invalid State via isStateValid if the partial densities of any mass scalars are < 0.

2.) Ensure we enforce a partial density floor for mass scalars while doing hydro. We already do this while doing chemistry (via the small_x param in Microphysics)

[psharda]

@BenWibking , regarding point 2 above, this line seems to enforce positivity for all scalars when it enforces the density floor:

quokka/src/hydro_system.hpp

Line 711 in d17b5e4

state[bx](i, j, k, scalar0_index + n) *= rho / rho_new;

[BenWibking]

Yes but it only triggers when the total density is negative, not when only the mass scalars are negative.

[BenWibking]

/azp run

[psharda]

/azp run