Reorganise settingtypes.txt (minetest#12490)

This organises the settingstype.txt file to use a logical/user-friendly structure. Advanced settings are also demoted to an advanced section at the end.

At most 3 levels of hierarchy are used, as that's the most allowed by the settings redesign

builtin/mainmenu/dlg_settings_advanced.lua

@@ -351,9 +351,9 @@ local function parse_config_file(read_all, parse_mods)
  local file = io.open(path, "r")
  if file then
  if not games_category_initialized then
- fgettext_ne("Games") -- not used, but needed for xgettext
+ fgettext_ne("Content: Games") -- not used, but needed for xgettext
  table.insert(settings, {
- name = "Games",
+ name = "Content: Games",
  level = 0,
  type = "category",
  })
@@ -384,9 +384,9 @@ local function parse_config_file(read_all, parse_mods)
  local file = io.open(path, "r")
  if file then
  if not mods_category_initialized then
- fgettext_ne("Mods") -- not used, but needed for xgettext
+ fgettext_ne("Content: Mods") -- not used, but needed for xgettext
  table.insert(settings, {
- name = "Mods",
+ name = "Content: Mods",
  level = 0,
  type = "category",
  })