Produce multi-arch docker images

[dgrove-oss]

We use a custom distDocker gradle task through the OpenWhisk project.

We should upgrade this task to support building/pushing proper multi-arch images (ie, both amd64 and arm64) to make it easier to develop OpenWhisk on modern Macs.

[dgrove-oss]

@shawnallen85 has a PR open for runtime-dotnet. After it merges and we verify the GitHub Actions are publishing multi-arch runtime-dotnet images as expected we can look into propagating the improvement across all of our runtime projects and applying it here too.

[shawnallen85]

https://hub.docker.com/r/openwhisk/action-dotnet-v6.0/tags

Looks like we have both arm64 and amd64 architectures published to docker hub.