feat: Added xonsh shell support - try 2

[anki-code]

Resolve #4622

Test:

docker run --rm -it rust

apt update && apt install -y python3 python3-pip
pip install --break-system-packages xonsh
xonsh

git clone -b xonsh_shell https://github.com/anki-code/rustup
cd rustup/

# https://rust-lang.github.io/rustup/dev-guide/
cargo build
mkdir home
$RUSTUP_HOME='home' $CARGO_HOME='home' target/debug/rustup-init --no-modify-path -y
source /rustup/home/env.xsh

$PATH.pop(0)  # remove '/usr/local/cargo/bin' from container
which cargo
# /rustup/home/bin/cargo
cargo --version
# cargo 1.91.1

[djc]

You added a merge commit again. Please squash.