Import GWSkyNet only at task level
Importing the GWSkyNet package is slow and leads to any gwcelery command hanging for a few seconds before printing
2023-05-18 21:42:09.771099: I tensorflow/core/platform/cpu_feature_guard.cc:182] This TensorFlow binary is optimized to use available CPU instructions in performance-critical operations.
To enable the following instructions: AVX2 FMA, in other operations, rebuild TensorFlow with the appropriate compiler flags.
This MR imports it only at the task level, similar to embright in !1148 (merged). I've added FIXMEs to remove this later if the gwskynet import is sped up.