Adopt shared zizmor workflow

[opentelemetrybot]

Adds zizmor scanning through the OpenTelemetry shared workflow.

The workflow uploads zizmor results to GitHub code scanning. After this PR merges, maintainers should:

1. Open the merged commit's Actions checks and confirm the Zizmor workflow succeeded on the default branch.
2. Open Security > Code scanning in this repository and confirm zizmor analyzed the merged commit.
3. Confirm the analysis has no high or critical security findings and no error-level findings.
4. Mark the corresponding admin PR ready for review, approve and merge it. After it merges, the repository ruleset requires a current zizmor analysis and blocks findings at those thresholds.
5. On the next repository PR, confirm GitHub reports a required zizmor code-scanning result.

If enforcement unexpectedly blocks a valid change, restore require_zizmor = false in open-telemetry/admin. Keep the zizmor workflow enabled so findings remain visible.

[github-advanced-security]

You are seeing this message because GitHub Code Scanning has recently been set up for this repository, or this pull request contains the workflow file for the Code Scanning tool.

What Enabling Code Scanning Means:

• The 'Security' tab will display more code scanning analysis results (e.g., for the default branch).
• Depending on your configuration and choice of analysis tool, future pull requests will be annotated with code scanning analysis results.
• You will be able to see the analysis results for the pull request's branch on this overview once the scans have completed and the checks have passed.

For more information about GitHub Code Scanning, check out the documentation.