Add Rainwater Path Diagnostic

[erphamucsd]

Purpose

Implementing rainwater path as a diagnostic variable.

To-do

Content

• Implemented RWP in core_diagnostics.jl.
• Add as a diagnostic for "config/model_configs/prognostic_edmfx_dycoms_rf02_column.yml".

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• I have read and checked the items on the review checklist.

[erphamucsd]

Closed and reopened because the branch was renamed to better fit the naming convention. Suggestions from previous PR have been added/committed to this branch.

[akshaysridhar]

Suggested change

	units = "kg m-2",
	units = "kg m^-2",

[akshaysridhar]

Closed and reopened because the branch was renamed to better fit the naming convention. Suggestions from previous PR have been added/committed to this branch.

@erphamucsd On the TODO block above : the pattern moving forward will rely on reducing dependency on cache variables - so, instead of precomputing q_rai we will use the specific function if necessary to get quantities from prognostic state variables. LazyBroadcast may also help with faster gpu code; you're using scratch space here so this is not strictly necessary.