Support multiple build support modules

[cryptiklemur]

Context
In order to reduce complexity in CI/CD configs (less steps, less matrixes, less cache,
it would be nice if we could get game-ci/unity-builder to install modules for more than one targetPlatform.

Additional details

My use case: I'm working on a mod for RimWorld, that builds AssetBundles. The script i've created to do this can take a buildTarget as an argument. If one isn't passed, it will create do all three.

      - name: Build Windows AssetBundles
        if: steps.copyassets.outputs.hasAssets == 'true'
        uses: game-ci/unity-builder@v4
        continue-on-error: false
        timeout-minutes: 30
        env:
          UNITY_LICENSE: ${{ secrets.UNITY_LICENSE }}
          UNITY_EMAIL: ${{ secrets.UNITY_EMAIL }}
          UNITY_PASSWORD: ${{ secrets.UNITY_PASSWORD }}
        with:
          unityVersion: 2022.3.35f1
          targetPlatform: StandaloneWindows64
          projectPath: AssetBuilder
          versioning: None
          allowDirtyBuild: true
          buildMethod: ModAssetBundleBuilder.BuildBundles
          customParameters: "-source=../RimworldCosmere/${{ matrix.mod }} -buildTarget=windows"
      - name: Build Mac AssetBundles
        if: steps.copyassets.outputs.hasAssets == 'true'
        uses: game-ci/unity-builder@v4
        continue-on-error: false
        timeout-minutes: 30
        env:
          UNITY_LICENSE: ${{ secrets.UNITY_LICENSE }}
          UNITY_EMAIL: ${{ secrets.UNITY_EMAIL }}
          UNITY_PASSWORD: ${{ secrets.UNITY_PASSWORD }}
        with:
          unityVersion: 2022.3.35f1
          targetPlatform: StandaloneOSX
          projectPath: AssetBuilder
          versioning: None
          allowDirtyBuild: true
          buildMethod: ModAssetBundleBuilder.BuildBundles
          customParameters: "-source=../RimworldCosmere/${{ matrix.mod }} -buildTarget=mac"
      - name: Build Linux AssetBundles
        if: steps.copyassets.outputs.hasAssets == 'true'
        uses: game-ci/unity-builder@v4
        continue-on-error: false
        timeout-minutes: 30
        env:
          UNITY_LICENSE: ${{ secrets.UNITY_LICENSE }}
          UNITY_EMAIL: ${{ secrets.UNITY_EMAIL }}
          UNITY_PASSWORD: ${{ secrets.UNITY_PASSWORD }}
        with:
          unityVersion: 2022.3.35f1
          targetPlatform: StandaloneLinux64
          projectPath: AssetBuilder
          versioning: None
          allowDirtyBuild: true
          buildMethod: ModAssetBundleBuilder.BuildBundles
          customParameters: "-source=../RimworldCosmere/${{ matrix.mod }} -buildTarget=linux"

I could clean this up into a single step, that doesn't have to deal with a matrix (which was my next plan) and artifact upload/download, or taking up a ton of disk space