Remove hacks from darwin nix purge script (#18656)

## Summary
In this commit we : 
- instead of `cd` to `/Library/LaunchDaemons` and then attempting to `launchctl unload` the nixos plist files we just pass the full path to unload as seen in `nix` documentation here : https://nixos.org/manual/nix/stable/installation/uninstall.html#:~:text=Stop%20and%20remove%20the%20Nix%20daemon%20services%3A

- move killing a process by prompting for confirmation to a new shell script as per feedback from previous PR : https://github.com/status-im/status-mobile/pull/18192#discussion_r1439495310

- fix few small typos

## Platforms
- macOS

nix/scripts/kill_proc_prompt.sh

@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+set -Eeuo pipefail
+# script to prompt user for terminating a process
+
+pid="${1}"
+
+read -p "Do you want to terminate this process? (y/n): " choice
+if [[ "${choice}" == "y" ]]; then
+    sudo kill "${pid}"
+    echo "Process ${pid} terminated."
+else
+    echo "Process not terminated. Please close it manually and retry."
+    exit 1
+fi

nix/scripts/purge.sh

@@ -22,12 +22,10 @@ nix_purge_linux_multi_user_users() {
 }
 
 nix_purge_darwin_multi_user_service() {
-    cd /Library/LaunchDaemons
-    NIX_SERVICES=(org.nixos.darwin-store.plist org.nixos.nix-daemon.plist)
-    for NIX_SERVICE in "${NIX_SERVICES[@]}"; do
-        sudo launchctl unload "${NIX_SERVICE}" || true
-        sudo launchctl remove "${NIX_SERVICE}" || true
-    done
+    sudo launchctl unload /Library/LaunchDaemons/org.nixos.nix-daemon.plist
+    sudo rm /Library/LaunchDaemons/org.nixos.nix-daemon.plist
+    sudo launchctl unload /Library/LaunchDaemons/org.nixos.darwin-store.plist
+    sudo rm /Library/LaunchDaemons/org.nixos.darwin-store.plist
 }
 
 nix_purge_darwin_multi_user_users() {
@@ -48,18 +46,10 @@ nix_purge_darwin_multi_user_volumes() {
 
         # Identify the process using the volume
         local pid=$(lsof +D /nix | awk 'NR==2{print $2}')
-        if [ -n "$pid" ]; then
+        if [[ -n "$pid" ]]; then
             echo "The volume /nix is in use by process ID $pid."
+            "${GIT_ROOT}/nix/scripts/kill_proc_prompt.sh" "${pid}" || return 1
 
-            # Ask the user whether to terminate the process
-            read -p "Do you want to terminate this process? (y/n): " choice
-            if [[ $choice == "y" ]]; then
-                sudo kill $pid
-                echo "Process $pid terminated."
-            else
-                echo "Process not terminated. Please close it manually and retry."
-                return 1
-            fi
         else
             echo "No process found using /nix. Manual intervention required."
             return 1
@@ -71,9 +61,9 @@ nix_purge_darwin_multi_user_volumes() {
 
 nix_purge_multi_user() {
     if [[ $(uname -s) == "Darwin" ]]; then
-        nix_purge_darwin_multi_user_service || true
-        nix_purge_darwin_multi_user_users || true
-        nix_purge_darwin_multi_user_volumes || true
+        nix_purge_darwin_multi_user_service
+        nix_purge_darwin_multi_user_users
+        nix_purge_darwin_multi_user_volumes
     else
         nix_purge_linux_multi_user_service
         nix_purge_linux_multi_user_users
@@ -117,7 +107,7 @@ if (return 0 2>/dev/null); then
     return
 fi
 
-# Confirm user decission, unless --force is used.
+# Confirm user decision, unless --force is used.
 if [[ "${1}" != "--force" ]]; then
     echo -e "${YLW}Are you sure you want to purge Nix?${RST}" >&2
     read -p "[y/n]: " -n 1 -r
@@ -129,7 +119,7 @@ if [[ "${1}" != "--force" ]]; then
 fi
 
 NIX_INSTALL_TYPE=$(nix_install_type)
-# Purging /nix on NixOS would be disasterous.
+# Purging /nix on NixOS would be disastrous.
 if [[ "${NIX_INSTALL_TYPE}" == "nixos" ]]; then
     echo -e "${RED}You should not purge Nix files on NixOS!${RST}" >&2
     exit