core.common: move away import related stuff to my.core.utils.imports

moving without backward compatibility, since it's extremely unlikely they are used for any external modules

in fact, unclear if these methods still have much value at all, but keeping for now just in case

my/core/hpi_compat.py

@@ -101,7 +101,7 @@ Please install {' '.join(requires)} as PIP packages (see the corresponding READM
 def _get_dal(cfg, module_name: str):
     mpath = getattr(cfg, module_name, None)
     if mpath is not None:
-        from .common import import_dir
+        from .utils.imports import import_dir
 
         return import_dir(mpath, '.dal')
     else: