feat: add support for base64 encoded docker password

[nianyush]

No description provided.

[nianyush]

@Itxaka @mudler Can you help to review this? For GCR registry, its service token is a json file which doesnt work well to directly pass it through github inputs unless i base64 encoded it

[nianyush]

By adding this, we can just run the action with pretend: true for the first time to generate a matrix of packages to be built, and then use that matrix in github workflow to build all those packages in parallel

[nianyush]

Like this

name: Reusable Publish


jobs:
  generate-packages:
    runs-on: ubuntu-latest
    outputs:
      packages: ${{ steps.packages.outputs.packages }}
    steps:
    - uses: actions/checkout@v4
      with:
        fetch-depth: 0
    - name: Set up QEMU
      uses: docker/setup-qemu-action@v3
    - name: Set up Docker Buildx
      uses: docker/setup-buildx-action@v3
    - name: Prepare
      id: prepare
      run: |
        mkdir build
    - name: Download meta 🔧
      uses: nianyush/luet-github-action@docker-password-base64
      with:
        FINAL_REPO: ${{ inputs.image_repo }}
        REPOSITORY_TYPE: docker
        downloadAllMeta: true
        downloadFromList: false
        downloadMeta: true
        # renovate: datasource=github-releases depName=mudler/luet
        luetVersion: 0.36.0
    - name: Generate packages 🔧
      uses: nianyush/luet-github-action@docker-password-base64
      id: packages
      with:
        build: true
        buildx: true
        pretend: true
  build:
    runs-on: ubuntu-latest
    needs: [generate-packages]
    strategy:
      matrix: ${{ fromJson(needs.generate-packages.outputs.packages) }}
    env:
      ARCH: ${{ inputs.arch }}
    steps:
    - uses: actions/checkout@v4
      with:
        fetch-depth: 0
    - name: Set up QEMU
      uses: docker/setup-qemu-action@v3
    - name: Set up Docker Buildx
      uses: docker/setup-buildx-action@v3
    - name: Prepare
      id: prepare
      run: |
        mkdir build
    - name: Download meta 🔧
      uses: nianyush/luet-github-action@docker-password-base64
      with:
        FINAL_REPO: ${{ inputs.image_repo }}
        REPOSITORY_TYPE: docker
        downloadAllMeta: true
        downloadFromList: false
        downloadMeta: true
        # renovate: datasource=github-releases depName=mudler/luet
        luetVersion: 0.36.0
    - name: Build packages 🔧
      uses: nianyush/luet-github-action@docker-password-base64
      with:
        CURRENT_PACKAGE: ${{ matrix.package }}
        build: true
        buildx: true
        platform: linux/${{ inputs.arch }}