Standardize Attestation Artifact Names and Permissions

What does this MR do?

Changes final attestation file name and permission

Why was this MR needed?

To make the file more easily discoverable and accessible

What's the best way to test this MR?

Run a job

print variables:
  script:
    - echo HI > text.txt
  artifacts:
    name: test
    paths:
      - text.txt
  tags:
    - shell-local

The file name should be test-metadata.json

If you remove the artifact name it should be artifacts-metadata.json.

What are the relevant issue numbers?

Closes #29152 (closed)