Commit a8730c51c8 moved the enum
utils from libnm-core to shared/nm-utils.
However, three of those functions are part of public API in libnm.
So, when statically linking against "shared/nm-utils/nm-enum-utils.c"
and dynamically linking against libnm.so, those symbols are present
twice and cause a linker failure.
Fix that by moving the public API back to libnm-core.
Fixes: a8730c51c8
libnm contains the public function nm_utils_enum_from_str() et al.
The function is not flexible enough for nmcli's usecase. So, I would
need another public function like nm_utils_enum_from_str_full() that
has an extended API.
That was already required previously for ifcfg-rh writer, but in that
case I could just add it as internal API as libnm-core is linked statically
with NetworkManager.
I don't want to commit to a public API for an utility function. So move
the code instead to the shared directory, so that nmcli may link
statically against it and use the internal API.
