test: improve test workflow to reduce boilerplate

[abannachGrafana]

• test: update test workflow to check for fork as prerequisite
• chore(zizmor): fix zizmor finding and comment on template injection of action
• test: update fork check to include push event to main
• test: remove ref and incorrect event methods
• chore: remove unused workflow

[Copilot]

Pull Request Overview

This PR aims to improve the test workflow by reducing boilerplate and ensuring that tests are only run on non-forked repositories. Key changes include:

• Adding a new "check-not-fork" job to determine if the action is triggered from a fork.
• Updating various test jobs to depend on the "check-not-fork" job.
• Modifying a comment in action.yml regarding template injection via environment variables and updating permissions in the automerge-dependabot workflow.

Reviewed Changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 2 comments.

File	Description
action.yml	Updated comment addressing template injection and env var handling.
.github/workflows/test.yml	Added fork check job and linked it as a dependency to multiple test jobs.
.github/workflows/automerge-dependabot.yml	Moved permissions under the job definition to align with intended access.

Files not reviewed (1)

• .github/workflows/ci.yml: Language not supported