feat: respect `/etc/timezone`, `/etc/localtime`, `TZ` like `ls` and `exa` does

[fox91]

Being used to the ls output and having used exa which reproduced it (in my opinion) correctly, I believe there is a bug in the eza output. In the examples below you can see how the modification date of the baz file is shown differently in eza, as if it did not take into account the daylight savings time changes during the year. The time that is shown is not incorrect, it is simply shown in the current timezone (UTC+1) instead of taking into account the time changes present in the selected timezone (Europe/Rome in this case).

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 20.04.6 LTS
Release:        20.04
Codename:       focal

$ uname -a
Linux pcname 5.4.0-166-generic #183-Ubuntu SMP Mon Oct 2 11:28:33 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux

$ cat /etc/timezone 
Europe/Rome

$ ls --version
ls (GNU coreutils) 8.30

$ ls -lAF --full-time
total 0
-rw-r--r-- 1 user group 0 2023-02-04 10:35:00.000000000 +0100 bar
-rw-r--r-- 1 user group 0 2023-06-04 10:35:00.000000000 +0200 baz
-rw-r--r-- 1 user group 0 2023-11-12 10:35:00.000000000 +0100 foo

$ exa --version
v0.10.1 [+git]

$ exa -aglF --time-style full-iso
.rw-r--r-- 0 user group 2023-02-04 10:35:00.000000000 +0100 bar
.rw-r--r-- 0 user group 2023-06-04 10:35:00.000000000 +0200 baz
.rw-r--r-- 0 user group 2023-11-12 10:35:00.000000000 +0100 foo

$ eza --version
v0.15.3 [+git]

$ eza -aglF --time-style full-iso
.rw-r--r-- 0 user group 2023-02-04 10:35:00.000000000 +0100 bar
.rw-r--r-- 0 user group 2023-06-04 09:35:00.000000000 +0100 baz
.rw-r--r-- 0 user group 2023-11-12 10:35:00.000000000 +0100 foo