[helper][windows] bash support for gitlab-helper image

What does this MR do?

• Add bash(busybox) to GitLab helper image on windows (x64)

Why was this MR needed?

GitLab currently supports pwsh across all environments. This would allows one to use bash scripting across windows and Linux environments.

What's the best way to test this MR?

Update the runner config to point

[[runners]]
  name = "w11-docker-bash"
  executor = "docker-windows"
  shell = "bash"
  ...
  [runners.docker]
    # image with bash built into it
    image = "localhost/base"
    helper_image = "localhost/gitlab_helper:latest"
    pull_policy = ["if-not-present"]
    ...

[[runners]]
  name = "w11-docker-pwsh"
  executor = "docker-windows"
  shell = "pwsh"
  ...
  [runners.docker]
    image = "mcr.microsoft.com/powershell:lts-windowsservercore-ltsc2022"
    helper_image = "localhost/gitlab_helper:latest"
    pull_policy = ["if-not-present"]
    ...

What are the relevant issue numbers?

!3503 (closed) #4725 (closed)