UM Read Radaer loads numerous configuration files for parsing on every rank

UM Read Radaer is reading the same file on every rank, within an ensemble member and across ensembles

this is a problematic pattern for scaling on parallel file systems

e.g. `lut/nml_ac_lw`
`('_OPEN', 'um_read_radaer_lut$um_read_radaer_lut_mod_', 'um_radaer_lut_init$um_radaer_lut_init_mod_'): 1176`
for 588 ranks

lut/nml_ac_sw, lut/nml_an_lw,

Consider providing a rad pattern that either uses:

MPI-IO to conduct collective reads
Reads on Rank0 and distributes to ranks using MPI