Add a helper function to check if the user is root. This function can be
useful for the prompts for example. Modify the prompts made root checked
to use the function instead. Add also the support of Administrator like
a root user.
Fixes: #7031
This runs build_tools/style.fish, which runs clang-format on C++, fish_indent on fish and (new) black on python.
If anything is wrong with the formatting, we should fix the tools, but automated formatting is worth it.
Currently fish doesn't recognize toor as special. However, it's likely
that on BSD systems, fish shell will be used on toor, not on root (toor
is an intentionally existing account to use more advanced shell on, like
shell).
When you chroot in Debian, bash shows the chroot environment in the prompt:
```bash
...
if [ -z "${debian_chroot:-}" ] && [ -r /etc/debian_chroot ]; then
debian_chroot=$(cat /etc/debian_chroot)
fi
PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w\$ '
...
```
This is the effect:
```
(chroot_env) user@host:~#
```
It is useful when chrooting, since usually the hostname remains the same and thus you can't distinguish where you are.
