Move the public functions from the editors/object (`ED_object.hh`)
header to the `blender::ed::object` namespace, and move all of the
implementation files to the namespace too. This provides better code
completion, makes it easier to use other C++ code, removes unnecessary
redundancy and verbosity from local uses of public functions, and more
cleanly separates different modules.
See the diff in `ED_object.hh` for the main renaming changes.
Pull Request: https://projects.blender.org/blender/blender/pulls/119947
