Set gas-species profiles in TUV-x prior to calculating rate constants

[mattldawson]

Update the concentrations of radiatively active gas-phase species in TUV-x prior to calculating photolysis rate constants.

@peverwhee - TUV-x needs to know the concentrations of certain chemical species above the top of the model. Is there a way to set this value for a constituent?

(related issue on CCPP-framework: NCAR/ccpp-framework#573)

Acceptance Criteria

• Gas-phase species can be configured to be included in the TUV-x solving for the radiation field.
• The concentrations above the model top can be configured to be estimated using a scale height, or read in from a file
• TUV-x photolysis rate constants are calculated using the actual concentrations of total air density and each specified gas-phase species for each column at each timestep

Ideas

• Identify CCPP standard name for air density
• Use constituents_t type to update species concentrations
• Follow the logic of the TUV-x PR into CAM: https://github.com/ESCOMP/CAM/blob/c12d1e46e0fdc1dccb0a651a6c9fefd6bb80b2ba/src/chemistry/mozart/mo_tuvx.F90#L1508-L1619

Questions

• Can we enable users to create profile and set the values for them?
• The indexing of the constituents is not guaranteed to be the same as what we set in micm_register() . We might need to add an initialization step where we look up the indices of chemical species (fixed and variable)