Address most thread safety issues in NR UE

csiim_vars/csirs_vars used to be global array for each UE. Now its present in phy_data which is in dynamically allocated memory.

MAC config was done without mutex while DL and UL threads could be running at the same time.

get_ue_nas_info was allocating memory possibly from more than one thread. Moved it into new init function for UE NAS layer.

Addreses most issues in #869