Enable Multi-Platform Support for kubemacpool Image Builds

[ashokpariya0]

These changes enable building and pushing kubemacpool container images for multiple platforms (amd64, s390x, arm64) from a single Dockerfile. Enhanced multi-platform support in the build process by adding a PLATFORMS argument in the Makefile for amd64, s390x, and arm64 architectures. Multi-platform build support is provided for both Docker and Podman container runtimes.

What this PR does / why we need it:
The upstream kubemacpool image (link) currently supports only the amd64 architecture. The proposed changes in this PR enable multi-platform support for the kubemacpool image, broadening its compatibility to include additional architectures.

Special notes for your reviewer:
Multi-platform build support is enabled for both Docker and Podman container runtimes, and the necessary changes have been made accordingly.
The PLATFORMS variable defines the target platforms for building the manager image, allowing support for multiple architectures.

To use this feature, you need to:

For Docker:

Have access to docker buildx. More information: [Docker Buildx Documentation](https://docs.docker.com/build/building/multi-platform/)
Ensure that BuildKit is enabled. More information: [Docker BuildKit Enhancements](https://docs.docker.com/develop/develop-images/build_enhancements/)
For Podman:

No additional dependencies are required to build multi-platform images. Podman supports this feature natively.

Release note:

None

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