barretenberg nightly build failing

[kevaundray]

Problem

Barretenberg releases nightly builds each day, however these are currently failing due to npm publish not being idempotent.

The releases use the same workflow as publishing, and as a part of publishing, we push packages to npm. Since the version number in package.json may not change each night, it will cause the workflow to fail.

Solution

Short term

• Not publish to npm when running nightly builds

Long term

• Publish to npm and tag each version with the timestamp.
• Also possibly add a cron job each month that removes all npm releases that are more than a month old.

[kevaundray]

I've added a skip if nightly clause in #1837 -- leaving this open because we ideally want to get nightly builds of the bb.js packages too