[in-toto] Add provenance extension to Jenkins plugin

[nate-double-u]

The in-toto Jenkins plugin allows users to generate in-toto link metadata in their build pipelines. However, with ITE-6 and the in-toto Attestations project, the plugin must also be capable of generating other in-toto attestations such as the provenance specification. The aim of this project is to refactor the Jenkins plugin to allow for new attestation types, as well as to implement the provenance attestation. The in-toto-java implementation can be leveraged to create the new attestations in the Jenkins plugin.

Mentor(s): Aditya Sirish (@adityasaky), Santiago Torres-Arias (@SantiagoTorres)

https://github.com/cncf/mentoring/blob/main/summerofcode/2022.md#add-provenance-extension-to-jenkins-plugin