Make release CI more robust

[chivalryq]

Now there are two weaknesses in release CI:

1. Checking chart version before building images: https://github.com/oam-dev/cluster-gateway/blob/master/.github/workflows/go-release.yml#L35.

This causes several pre-release failure:

• https://github.com/oam-dev/cluster-gateway/actions/runs/3844678538
• https://github.com/oam-dev/cluster-gateway/actions/runs/3827369890
• https://github.com/oam-dev/cluster-gateway/actions/runs/3637240597

This is a great check. However, its success relies that the maintainers remember to modify the chart version. We can make the chart version a placeholder and replace it in CI.

2. The ACR domain isn't correct: https://github.com/oam-dev/cluster-gateway/blob/master/.github/workflows/go-release.yml#L72

This make the recent v1.7.0 release fail and no arm64 image builded and pushed.

Besides, there is also a suggestion: use --platform argument to distinguish the image platforms rather than including platform in tag. GitHub Action like docker/build-push-action@v2 can help with that. This makes developers' lives easier. 🙏