Add a flag for cold starting LSMs distinct from generic flag for restarts

[grantfirl]

Description

In order to use the SCM with the RUC LSM and to initialize the RUC LSM-specific variables from data, we need to add a new logical variable that denotes whether the LSM is being cold-started or not. The use of the current "flag_for_restart" variable in physics is not sufficient because it is used for many schemes in addition to the RUC LSM and the SCM can be initialized in a "partial restart" configuration where we have initialization/restart data for the LSM, but not necessarily for the other physics.

Solution

Create a lsm_cold_start variable. For UFS, this can just be equal to (.not. flag_for_restart) and nothing will change. For the SCM, using this flag allows the initialization of RUC LSM directly from variables it expects (and not from 4-level Noah-based data) while leaving the rest of physics schemes in cold start.