fontconfig: update 2.10.2 -> 2.11.1

Reference: #2050 

- Retained fontconfig_210
- Search for configs under `/etc/fonts/2.11`
- Use `$fontconfig/etc/fonts.conf` instead of `/etc/fonts/fonts.conf`
- Move nix profile share/fonts and lib/X11/fonts from nixos to `makeFontsConf`. This allows applications using `makeFontsConf`, nixos and non-nixos to find fonts in the nix profile in all cases.

**Nixos**

- `/etc/fonts/2.11/conf.d/00-nixos.conf` is being created with options plus <dir> for each font.
- For backward-compatibility `/etc/fonts/fonts.conf` is created for fontconfig 2.10.

**Non-nixos**

- Applications with fontconfig 2.10 keeps working as they read the system `/etc/fonts/fonts.conf`.
- Applications with fontconfig 2.11 will have no fonts. Either install some font with nix-env or set `FONTCONFIG_FILE=/etc/fonts/fonts.conf`