Sponge layer improvment

Introduced changes:

• zonal sponge layer : zonal mean doesn't need to be compute at each call (performance improvment)
• zonal mean can is saved in restart for safe restarting
• Implementation of sponge layer based on exponential moving average, no need to compute zonal mean

Testing checklist:

• Gitlab CI
• GPU/JeanZay
• modipsl/LAM (mr7_compare_ICO_start_01_29.pdf, mr7_compare_ICO_restart_01_29.pdf)