Add disp_name member to FmPath object to move it from FmFileInfo.

Also add internal APIs _fm_path_[sg]et_display_name() to check and
reset it.
Move disp_name data from FmFileInfo into FmPath.

We don't lose anything since almost every FmPath has appropriate
FmFileInfo but since FmPaths are reusable we may also get some
benefit. Another benefit is fm_path_display_basename() now will
show real display name which have charset in account (from GIO)
instead of our own estimation.
Ignore second argument from fm_path_display_name() - it caused problems.

If we want not displaying name but displayable version of file name
then we should use g_file_get_parse_name() as it was clearly stated
in GIO documentation because that will take into account specific rules
for file names in target file system, we cannot do it ourselves.
Deprecate fm_get_user_input_path() - it is not reliable and never used.
Revive fm_path_new_for_display_name() API.

It can be made reliable using g_file_get_child_for_display_name()
as it was stated in FIXME long time ago.
Use display name to change path from FmPathEntry.
FmFileInfoJob should recursively set display names for path parents.

If we entered a new path in path entry (or copy-pasted it) we can get
new FmPath parents with unresolved display names. This rare case should
be checked and resolved by FmFileInfoJob.