Adding support for ppc64le platform using Multi-arch GitHub Actions flow

[Sunidhi-Gaonkar1]

This PR is in reference to #613 to provide quay.io/ansible/receptor:devel image for Power (ppc64le) platform.
I have modified the GitHub Action workflows to use docker buildx tool to cross compile docker images for ppc64le and produce multiarch image. I have tested the workflows in my fork repository and mentioned below are the links for the same.

1. devel_image.yml workflow:

• Link for GitHub Actions: https://github.com/Sunidhi-Gaonkar1/receptor/actions/runs/2590090642
• Link for the image : https://quay.io/repository/siddhesh_ghadi/ansible_receptor?tab=tags&tag=devel

2. stage.yml workflow:

• Link for GitHub Actions: https://github.com/Sunidhi-Gaonkar1/receptor/actions/runs/2594580131
• Link for the image: https://github.com/Sunidhi-Gaonkar1/receptor/pkgs/container/receptor

3. promote.yml workflow:

• Link for GitHub Actions: https://github.com/Sunidhi-Gaonkar1/receptor/actions/runs/2594823333
• Link for the image: https://quay.io/repository/siddhesh_ghadi/ansible_receptor?tab=tags&tag=latest

This PR modifies 3 workflows (devel_image.yml , stage.yml and promote.yml) and can be extended for PR workflow as well.(if required)

[jwcroppe]

Thanks @Sunidhi-Gaonkar1.
@shanemcd and @fosterseth - any thoughts on this approach? Thanks in advance for your time!

[shanemcd]

Hello - thanks a lot for this contribution. I've rebased and extended this work in #652, which just merged.