Loosen restriction on optional arguments in CCPP.

[dustinswales]

Description

When optional arguments were added back into the CCPP as part of #189, all variables that were conditionally allocated on the host side were required to be defined as optional within the schemes. This restriction required host-model logic to be implicitly built into the schemes and metadata. For example, scheme variables that were optional in the context of the host model, but always required within the context scheme, still needed to be defined as optional within the scheme. This resulted in schemes having an arbitrary/confusing mis-match of required/optional arguments.

This PR contains changes to the CCPP Framework (PR627) and CCPP Physics (PR248), reducing the restrictions on optional arguments and corresponding schemes changes, respectively. (There is also a small bugfix for the LW Jacobian used by RRTMGP).

Issue(s) addressed

N/A

Testing

RTs pass on Hera using Intel
(Running the full set now and will updated with links to RT logs when they complete)

Dependencies

N/A

Requirements before merging

• All new code in this PR is tested by at least one unit test
• All new code in this PR includes Doxygen documentation
• All new code in this PR does not add new compilation warnings (check CI output)