Change OAI license to CSSL v1.0 (and others)

- all RAN code, CI code, configuration files, dockerfiles, in CSSL v1.0
- all deployment code (openshift, charts, ancillary files like shell
  scripts), in MIT
- documentation in CC-BY-4.0
- exceptions might apply and are listed in NOTICE
- there is a new LICENSES folder with all licenses
- CONTRIBUTIONS.md has been updated accordingly

For automated changes based on OAI PL v1.1:

    perl -i~ -0pe 's/\/\*.*Licensed to the OpenAirInterface.*openairinterface.org\n#?/\/*\n * SPDX-License-Identifier: LicenseRef-CSSL-1.0\n/s' **/*.{c,h,cpp}
    perl -i~ -0pe 's/\/\*.*Licensed to the OpenAirInterface.*openairinterface.org\n#?/\/*\n * SPDX-License-Identifier: LicenseRef-CSSL-1.0\n/s' **/*.ts
    perl -i~ -0pe 's/<!--.*Licensed to the OpenAirInterface.*openairinterface.org\n.*-->/<!-- SPDX-License-Identifier: LicenseRef-CSSL-1.0 -->/s' **/*.xml

The rest (cmake, files with missing license, cmake) manually.

doc/episys/lte_mode_l2_emulator/README.md

@@ -1,3 +1,5 @@
+<!-- SPDX-License-Identifier: CC-BY-4.0 -->
+
 There are fundamental changes to the L2 emulation mechanism; these changes allow the
 user to run multiple UEs in separate Linux processes/machines/VMs/etc. They use a separate
 entity between the UE(s) and eNB. The UEs use nFAPI to communicate with the eNB. The

doc/episys/nsa_mode_l2_emulator/README.md

@@ -1,3 +1,5 @@
+<!-- SPDX-License-Identifier: CC-BY-4.0 -->
+
 There are fundamental changes to the L2 emulation mechanism; these changes allow the
 user to run multiple UEs in separate Linux processes/machines/VMs/etc. They use a separate
 entity between the UE(s) and eNB/gNB. The UEs use nFAPI to communicate with the eNB/gNB. The