Reduce memory footprint

[sriharshakandala]

RRTMGP's memory footprint seems to be primarily dominated by (2) arrays, random_sw and random_lw.

test % julia --project all_sky_tuning.jl
FT = Float64, ncols = 131658; size per field = 0.04119899868965149 GB
"---------------------" = "---------------------"
CPU_slv_mem = 25.158858485519886 GB
"---------------------" = "---------------------"
fldname = context; fldsize = 0.0 GB
fldname = as; fldsize = 23.609969824552536 GB
fldname = op; fldsize = 0.12359713017940521 GB
fldname = src_lw; fldsize = 0.41591424494981766 GB
fldname = src_sw; fldsize = 0.3737342208623886 GB
fldname = bcs_lw; fldsize = 0.01569490134716034 GB
fldname = bcs_sw; fldsize = 0.029428035020828247 GB
fldname = fluxb_lw; fldsize = 0.1265399158000946 GB
fldname = fluxb_sw; fldsize = 0.16871988773345947 GB
fldname = flux_lw; fldsize = 0.1265399158000946 GB
fldname = flux_sw; fldsize = 0.16871988773345947 GB
"---------------------" = "---------------------"
fldname = lon; fldsize = 0.0 GB
fldname = lat; fldsize = 0.0 GB
fldname = p_lay; fldsize = 0.041199035942554474 GB
fldname = p_lev; fldsize = 0.04217996448278427 GB
fldname = t_lay; fldsize = 0.041199035942554474 GB
fldname = t_lev; fldsize = 0.04217996448278427 GB
fldname = t_sfc; fldsize = 0.000980965793132782 GB
fldname = col_dry; fldsize = 0.041199035942554474 GB
fldname = vmr; fldsize = 0.7827810272574425 GB
fldname = cld_r_eff_liq; fldsize = 0.041199035942554474 GB
fldname = cld_r_eff_ice; fldsize = 0.041199035942554474 GB
fldname = cld_path_liq; fldsize = 0.041199035942554474 GB
fldname = cld_path_ice; fldsize = 0.041199035942554474 GB
fldname = cld_frac; fldsize = 0.041199035942554474 GB
fldname = random_lw; fldsize = 10.546943709254265 GB
fldname = random_sw; fldsize = 9.228575751185417 GB
fldname = cld_mask_lw; fldsize = 1.3183680027723312 GB
fldname = cld_mask_sw; fldsize = 1.3183680027723312 GB
fldname = cld_mask_type; fldsize = 0.0 GB
fldname = ice_rgh; fldsize = 7.450580596923828e-9 GB
fldname = nlay; fldsize = 7.450580596923828e-9 GB
fldname = ncol; fldsize = 7.450580596923828e-9 GB
fldname = ngas; fldsize = 7.450580596923828e-9 GB
"---------------------" = "---------------------"
test %

Task:
Refactor the code to reduce memory footprint.