do_cmake: use Python 3.12 on ubuntu >= 24

do_cmake: use Python 3.12 on ubuntu >= 24

the "official" Python shipped along with Ubuntu 24.04 (Noble Numbat) is
Python 3.12. And some of our building have been upgraded to Ubuntu
24.04. But we are still using Python 3.10 on Ubuntu >= 22, this breaks
the build. And CMake fails like:

```
CMake Error at /usr/share/cmake-3.28/Modules/FindPackageHandleStandardArgs.cmake:230 (message):
  Could NOT find Python3 (missing: Python3_EXECUTABLE Python3_INCLUDE_DIRS
  Python3_LIBRARIES Interpreter Development Development.Module
  Development.Embed) (Required is exact version "3.10")

      Reason given by package:
          Interpreter: Wrong version for the interpreter "/bin/python3"

Call Stack (most recent call first):
  /usr/share/cmake-3.28/Modules/FindPackageHandleStandardArgs.cmake:600 (_FPHSA_FAILURE_MESSAGE)
  cmake/modules/FindPython/Support.cmake:3863 (find_package_handle_standard_args)
  cmake/modules/FindPython3.cmake:545 (include)
  CMakeLists.txt:597 (find_package)
```

This build failure should also happen on developers who build Ceph on
Ubuntu >= 24.

In this change, we use Python 3.12 on Ubuntu >= 24

Signed-off-by: Kefu Chai <tchaikov@gmail.com>