Automate Github release creation with a script

[antoninbas]

Describe what you are trying to solve
I currently create each release manually by following the steps documented in https://github.com/vmware-tanzu/antrea/blob/master/docs/maintainers/release.md. This can be error-prone (and tedious), and as the project grows, there may be additional tasks to perform to create a release.

Describe the solution you have in mind
The process can be refined over time. At the moment we can just create a script to perform the tasks listed in https://github.com/vmware-tanzu/antrea/blob/master/docs/maintainers/release.md, leveraging the Github API to create the release.

In the long term, the process could look like this:

• create a release candidate tag and push
• run validation tests on the release tag (this only makes sense if we need to run extra tests compared to CI).
• if tests pass, create a Github release from that release candidate. This can also be automated.

[antoninbas]

This is a step in the right direction: #517

[github-actions]

This issue is stale because it has been open 180 days with no activity. Remove stale label or comment, or this will be closed in 180 days

[github-actions]

This issue is stale because it has been open 180 days with no activity. Remove stale label or comment, or this will be closed in 180 days

[github-actions]

This issue is stale because it has been open 90 days with no activity. Remove stale label or comment, or this will be closed in 90 days