Changes

Ri_zm calc (Part 2) - Move the brunt_vaisala smoothing into calc_brunt_vaisala_freq_sqd (#1156)

CLUBB ticket #1145

Includes previous steps:
* First step: Move call to calc_bv
* Ri_zm calc (Part 1.5) - Adjusted signature of diagnose_Lscale_from_tau #1145

Newest changes: Ri_zm calc (Part 2) - Move brunt_vaisala smoothing into calc_brunt_vaisala_freq_sqd

`brunt_vaisala_frq_sqd_smth` is now calculated in subroutine `calc_brunt_vaisala_freq_sqd` and it is now written to disk in `advance_clubb_core` with all the other `brunt_vaisala` variables.

Unfortunately, I had to make a couple more changes since moving this calculation into `calc_brunt_vaisala_freq_sqd` meant that any subroutine involved in calling `calc_stability_correction` would need to get `l_modify_limiters_for_cnvg_test` fed in, because `calc_brunt_vaisala_freq_sqd` is also called in `calc_stability_correction`.

This commit is BIT_CHANGING since `brunt_vaisala_frq_sqd_smth` used to be all zeros before this change in Lscale mode and now it is actually calculated. BFB in taus code.