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/RRC/rrc-dev.md

@@ -1,3 +1,5 @@
+<!-- SPDX-License-Identifier: CC-BY-4.0 -->
+
 This document contains documentation for the 5G RRC layer, destined towards
 developers. It explains the basic working of the RRC, and various UE procedure
 schemes (connection, reestablishment, handover) including their interworking

doc/RRC/rrc-usage.md

@@ -1,3 +1,5 @@
+<!-- SPDX-License-Identifier: CC-BY-4.0 -->
+
 This document describes the basic functioning of the 5G RRC layer, describes
 the periodic output, and explains the various configuration options that
 influence its behavior.