Split get_profile_filename() into
- get_profile_filename_from_profile_name() (parameter: a profile name)
- get_profile_filename_from_attachment() (parameter: an attachment)

Currently both functions call get_profile_filename_orig() (formerly
get_profile_filename()) so the behaviour doesn't change yet.

The most important part of this commit is changing all
get_profile_filename() calls to use one of the new functions to make
clear if they specify a profile or an attachment/executable as
parameter.

As promised, the is_attachment parameter starts to get used in this
patch ;-)

Note: The get_new parameter (which I'll explain in the patch actually
using it) is set to True in all calls to the new functions.
The long term plan is to get rid of it in most cases (hence defaulting
to False), but that will need more testing.

(cherry picked from commit ec741424f81e152598035324b6fde604427e0a63)