chore(build): Pre-push temporary manifest with linux/amd64. Fixes #4062

[lippertmarkus]

This is pre-pushing a temporary manifest to DockerHub referencing the linux/amd64 images right after those are built so we can release earlier without having to wait for the long-running arm64 image builds. After all images finished building the temporary manifest is overwritten with a new one with references to all images for amd64, arm64 and windows.

Details:

1. Building and pushing all images for linux/amd64, e.g. argoproj/argoexec:v2.11-linux-amd64 - this will only take around 6minutes
2. Create and push the manifest and reference only the linux/amd64 images yet, e.g. argoproj/argoexec:v2.11 referencing only argoproj/argoexec:v2.11-linux-amd64 for now
3. When all other images for Windows and linux/arm64 finished building after 40mins, we update and push the manifest overwriting the one created before to reference all images now instead of only the linux/amd64 ones, e.g. override argoproj/argoexec:v2.11 now referencing argoproj/argoexec:v2.11-linux-amd64, argoproj/argoexec:v2.11-linux-arm64, argoproj/argoexec:v2.11-windows

Example run: https://github.com/lippertmarkus/argo/actions/runs/270351664

Checklist:

• Either (a) I've created an enhancement proposal and discussed it with the community, (b) this is a bug fix, or (c) this is a chore.
• The title of the PR is (a) conventional, (b) states what changed, and (c) suffixes the related issues number. E.g. "fix(controller): Updates such and such. Fixes #1234".
• I've signed the CLA.
• I have written unit and/or e2e tests for my change. PRs without these are unlikely to be merged. Not needed.
• My builds are green. Try syncing with master if they are not.
• My organization is added to USERS.md.

[alexec]

Is there any risk we're swapping reliability and ease of maintenance for speed?

[lippertmarkus]

The only risk I see is that there may be more Windows or ARM64 users in the future and some of them might rely on the images also being available as soon as a new version is released.

Another idea would be to automate the release process and run it after images are built. Then the time for image builds wouldn't matter anymore.

[alexec]

OK. Lets merge and see what happens.

[alexec]

Next master build: https://github.com/argoproj/argo/actions/runs/278832139