Telegraf Release Candidates, Nightlies, & Test Artifacts

The Telegraf project has decided to discontinue the creation of release candidates (RC) releases due to low value in generating bug reports and support conversations. Instead, InfluxData will provide Telegraf nightlies for users to test new features and fixes, as well as pull request artifacts that allow users to download and validate fixes through a CI process. These changes aim to improve the overall process of releasing updates to the Telegraf project.