5G-LENA ns-3 nr module

Supported platforms

This release has been tested on the following platforms:
- Arch Linux with g++-13 and clang-16.
- Ubuntu 20.04 with g++10.
- Ubuntu 22.04 with g++11 and 12 and clang-11 and 14.
- Ubuntu 23.04 with g++13.
- Ubuntu 23.10 (Mantic Minotaur) with clang-16.

Important news

- This release comes with a completely new PMI Type-I Single Panel codebook for MIMO.

- Performance optimizations were included for faster simulations.

- The code base is updated for C++ conformance and aligned with ns-3.42.

- Many bugs were fixed. One of them is significant, however it is limited to NR-U users.
  The interference events were counted incorrectly after a refactoring merged in nr-3.0.
  This caused the NrSpectrumPhy to change state prematurely due to sensing the channel
  as empty when there was a transmission with received power bigger than the threshold.

- We introduced two new CI jobs. The first to improve uniformization of commit messages.
  The second catches memory related bugs, allowing for us or contributors to fix them
  before finding them on the wild, crashing simulations or generating bogus results.

- Remember to follow the instructions from the README.md file, i.e., to checkout the correct release branch of both ns-3 and the NR module. The information about compatibility with the corresponding ns-3 release branch is stated in the `README.md` file.

New user-visible features

- A new MIMO Type-I Single Panel codebook is available in the NR module.
  The ``NrCbTypeOneSp`` codebook allows the MIMO model introduced in
  nr-3.0 to support up to 32 antenna ports and up to rank 4. See the
  ``cttc-nr-mimo-demo.cc`` file for an example on how to configure 
  the new codebook. More details are available at the nr-manual and Doxygen.

- Sub-band downsampling/upsampling techniques were implemented, allowing
  for much faster simulations using large antenna panels with many ports.