The absence of parenthesis confuses the gobject-introspection parser
for some reason, making it emit WP_BASE_DIRS_FLAG_SUBDIR_WIREPLUMBER
multiple times in the .gir file
This removes the previous hardcoding of this suffix and allows the
functions to be useful to other projects that use libwireplumber
and want to use this code to locate their data & config.
This makes things more consistent and allows us also to add more
search paths in the future if necessary.
Also, stop using g_module_build_path() because it's deprecated and
build the path manually. This obviously is not portable to Windows/Mac
or other exotic platforms, but portability is not important at this
point. PipeWire is also not portable beyond Linux & BSD.
This adds support for the system-wide locations for configuration and
data files, as defined by the XDG Base Directory Specification.
In addition, it adds two flag groups, CONFIGURATION and DATA, to the
base-dirs system, so that we don't have to hard-code the combinations
of flags everywhere.
