Add Nightly builds for merged PRs

[janewang]

What problem does your feature solve?

We would like to have better release process and an outcome from the discussion is we need nightly builds to run github actions necessary.

Nightly builds can help us identifies things that are broken during build time, but only visible when actually making a new release (e.g. dry-run only run during the release process, so if you fix things for the build job, dry-run may not necessarily be correct).

What would you like to see?

An automatic release process that make a nightly build available.

Open questions:

• How nightly builds work with cargo packages?
• What would the versioning look like?

What alternatives are there?

N/A