nml/eclm: Added snow_thermal_cond parameters

[kvrigor]

See:

• Added snow_thermal_cond parameters namelist_eCLM_spmode-template#1
• Model updates: eCLM with new snow thermal conductivity options; ParFlow with more CUDA13 fixes  TSMP2#124
• Snow thermal conductivity changes: Sturm1997 and Jordan1991 eCLM#101

Note that Jordan1991 is the original snow thermal conductivity parameterization and Sturm1997 is the new one.

[kvrigor]

@s-poll : the latest nml/eclm also carries this drv_in modification:

- calendar = "NO_LEAP"
+ calendar = "GREGORIAN"

Is this supposed to be a fix or an experimental change? Not sure if this should be merged or not.

[kvrigor]

I'm reverting the drv_in change to make this PR only modify these lnd_in values:

 snow_thermal_cond_method = 'Jordan1991'
 snow_thermal_cond_glc_method = 'Jordan1991'
 snow_thermal_cond_lake_method = 'Jordan1991'