Add 7.2 container dockerfiles and update existing images

- Add dedicated target docker files for 7.2, both RHEL and Ubuntu
- in existing dockerfiles, update to also build E2 SMs
- for UBI images, only the entitlements are necessary, the rest can be
  omitted (it is superfluous)

Signed-off-by: arora <sagar.arora@eurecom.fr>
Co-authored-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

docker/Dockerfile.base.ubuntu22

@@ -45,6 +45,11 @@ RUN apt-get update && \
        gcc-12 \
        g++-12 \
        xxd \
+       libpcre2-dev \
+       python3-dev \
+       bison \
+       flex \
+       m4 \
        # python3-pip for conf template generation
        python3-pip && \
     update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-12 100 --slave /usr/bin/g++ g++ /usr/bin/g++-12 && \