Rebase wav_import_export and wav_shel_inp onto dev/ufs-weather-model

Continue the cap alignment by replacing the dev/unified-derived
wav_import_export.F90 (990 changed lines -> ~100) and wav_shel_inp.F90
(282 -> ~30) with UFS's current versions plus explicit CESM patches.

wav_import_export.F90 CESM patch:
- advertise set unchanged: So_h and Sw_lasl stay disabled; Sw_Hs/Sw_t01/
  Sw_t0m1/Sw_thm diagnostic exports added under cesmcoupled
- import fills both interpolation endpoints (X0 and XN): CESM keeps
  use_cmeps=.false., so the classic time-interpolated forcing path needs
  both arrays (UFS fills only X0)
- UFS's coastal-coupling export blocks are guarded .not. cesmcoupled:
  their Sw_thm/Sw_t0m1 state lookups collide with the CESM diagnostic
  field names, and CalcTHM (degrees) silently overwrote the CESM export
  (radians from w3iogomd) -- caught as a wavImp_Sw_thm diff in cpl.hi
- casename import made unconditional (UFS guards it non-CESM but uses
  it unguarded; never compiled for CESM upstream)

wav_shel_inp.F90 CESM patch:
- shel config read from wav_in//inst_suffix (multi-instance aware)
  instead of ww3_shel.nml, with a clear abort when neither config exists
- notype=7 kept unconditional: CESM builds do not define W3_COU, and
  UFS's notype=6 would skip type-7 (coupling) output date processing

wav_shr_mod.F90: removed the multigrid module variable, orphaned after
the cap and import/export rebases dropped multigrid support (as UFS did).

Overall model/src diff vs dev/ufs-weather-model: 996+/1297- before,
~640+/500- after; remaining divergence is the CESM build system, the
CESM output/restart core (w3wavemd/w3iorsmd/w3iogomd), validated newer
develop physics, and the documented cap deltas.

Validated: ERS_Ld3.TL319_t232_wg37.GW_JRA (intel) exact-restart PASS
with cpl.hi and cpl.hx.ww3 bit-identical to the merge_develop reference
and ww3.hi identical except the known THM convention delta; MCC GW_JRA
(gnu) multi-instance all PASS.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: alperaltuntas