WIP: integration_2021_wk50_a

MR !1274 (closed) : L2 Emulator for NSA Mode
MR !1354 (merged) : Fix msg4 segfault
MR !1347 (merged) : nr pdcp: introduce a thread to do pdcp_data_ind
MR !1360 (merged) : Scope telnet fixes
next : 1300, 1352