Update rebase bot to create fresh Go mod updates

Background

Currently, in most of our carried repos, we have a series of commits from the rebase bot that update the go mod.

It would be better if we changed the commit to a Drop commit and instead, had a single commit that created/updates the go mod and vendor as required.

Steps

• Update bot to change go mod commit messages to drop
• Work out how it can update the go modules in a single commit
• Work out how to drop old go mod commits

Stakeholders

• Cluster Infra

Definition of Done

• Future rebases only contain a single commit for go mod updates and vendoring

• Docs

• N/A

• Testing

• N/A