feat: add Slack CLI command runner workflow and installer composite action

[ewanek1]

Summary

This PR builds upon #486. It continues iterating on the GitHub composite action and workflow that runs Slack CLI commands directly in CI/CD.

Notes on Changes

Added action inputs for common flags including verbose and CLI version

Re-running a workflow automatically enables verbose output

Removed the flag-parsing script in favor of direct command execution via slack ${{ inputs.command }}

Added --skip-update flag to prevent auto-updates during installation

Enabled SLACK_DISABLE_TELEMETRY variable so usage won’t bump up numbers in collecting metrics

Updated logging to match GitHub's logger

Moved major logic into action.yml as a proper composite action

Requirements

• [X] I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• [X] I've read and agree to the Code of Conduct.