Provide workaround for broken "g_utf8_collate_key_for_filename"

g_utf8_collate_key_for_filename provides some automatic smartness which is often not desired:

See this comments:

https://gitlab.gnome.org/GNOME/glib/-/issues/1344#note_1652000

In a nutshell, what the filename sorting does is to break the names into segments that are either words or numbers, and compare the words alphabetically, and the numbers numerically.

This issue is about the implementation of a workaround, until the issue is fixed upstream.

Related/Duplicate Thunar Issues: #68 (closed), #1015 (closed), #1656 (closed)

Use Case1

mkdir -p test && touch test/194P && touch test/196A && touch test/20P

Expected result (ls): 194P 196A 20P

Current result (thunar): 196A 194P 20P

What happens: g_utf8_collate_key_for_filename numerically compares 196, 194 and 20 and sorts the files in that order.

Use Case2

mkdir -p test && touch test/2OP && touch test/01Z && touch test/003

Expected result (ls): 003 01Z 2OP

Current result (thunar): 003 2OP 01Z

What happens: g_utf8_collate_key_for_filename extracts the numbers, drops any leading zeros and then compares the plain number 1, 2 and 3

Desired fix: Instead of doing that automatic smartness, the user should have the possiblity to use a xfconf flag to toggle between "plain sorting" (just like ls) and "smart sorting"