- 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>