atmos_phys0_20_002: Bring in acc directives to enable GPU runs in SIMA

[peverwhee]

Tag name: atmos_phys0_20_002
Originator(s): peverwhee

Description (include issue title and the keyword ['closes', 'fixes', 'resolves'] and issue number):
addresses #154
closes #325

List all namelist files that were added or changed: n/a

List all files eliminated and why: n/a

List all files added and what they do: n/a

List all existing files that have been modified, and describe the changes:
(Helpful git command: git diff --name-status development...<your_branch_name>)

M    schemes/rrtmgp/rrtmgp_lw_gas_optics.F90
M    schemes/rrtmgp/rrtmgp_lw_rte.F90
M    schemes/rrtmgp/rrtmgp_sw_gas_optics.F90
M    schemes/rrtmgp/rrtmgp_sw_rte.F90
- add acc directives

M    schemes/rrtmgp/rrtmgp_lw_gas_optics.meta
M    schemes/rrtmgp/rrtmgp_lw_rte.meta
M    schemes/rrtmgp/rrtmgp_sw_gas_optics.meta
M    schemes/rrtmgp/rrtmgp_sw_rte.meta
- add necessary dependencies for gpu runs

M    schemes/rrtmgp/rrtmgp_inputs_setup.meta
M    schemes/rrtmgp/rrtmgp_pre.meta
M    schemes/tropopause_find/tropopause_find.meta
- use units of "days" for all calendar day variables

M    schemes/rrtmgp/rrtmgp_sw_solar_var.F90
M    schemes/rrtmgp/rrtmgp_sw_solar_var.meta
- change standard name of "2" dimension from ccpp_constant_two to constant_dimension_two

List all automated tests that failed, as well as an explanation for why they weren't fixed: n/a

Is this an answer-changing PR? If so, is it a new physics package, algorithm change, tuning change, etc? no

If yes to the above question, describe how this code was validated with the new/modified features:

[nusbaume]

Thanks @peverwhee! I had one question about a directive, and a request to update the PR description, but otherwise this PR looks good to me!

[nusbaume]

Thanks for getting this working @peverwhee! I just had a couple requests for comments (but they don't require a re-review).

[jimmielin]

Thanks @peverwhee! Minor suggestions as promised