Guessing origin name is almost always wrong in the as_utils_install_metadata_file()

[mcrha]

The code looks like this right now:

			/* guess origin */
			tmp2 = g_strdup_printf ("_icons-%s.tar.gz", icons_size_id);
			tmp = g_strstr_len (basename, -1, tmp2);

There are couple problems with it:

• you expect file names as generated by the appstream-generator, but it names them:

-rw-r--r--. 1 user user  105 Nov 13 15:36 CID-Index-x86_64.json.gz
-rw-r--r--. 1 user user 1030 Nov 13 15:36 Components-x86_64.xml.gz
-rw-r--r--. 1 user user 1084 Nov 13 15:36 Components-x86_64.xml.xz
-rw-r--r--. 1 user user   29 Nov 13 15:36 icons-128x128@2.tar.gz
-rw-r--r--. 1 user user   29 Nov 13 15:36 icons-48x48@2.tar.gz
-rw-r--r--. 1 user user 2482 Nov 13 15:36 icons-48x48.tar.gz
-rw-r--r--. 1 user user   29 Nov 13 15:36 icons-64x64@2.tar.gz
-rw-r--r--. 1 user user 3506 Nov 13 15:36 icons-64x64.tar.gz

• you use an underscore, but a common "separator" is a dash character
• common name used to be appstream-icons.tar (with a dash), where the appstream is not the origin name.

I suggest to not guess, simply require the origin name to be provided by the caller.