Adds deployment access management features to the CLI

[ejacquier]

Summary

Adds deployment access management features to the CLI, allowing users to check their access status and request deployment access directly from the command line.

• Add cre account access command to check status and request deployment access
• Display deployment access status in cre whoami output
• Prompt users to request access when running cre workflow deploy without access
• Show deploy access hint after successful workflow simulation
• Add deploy access hint to global help template for gated users

Changes

New Command: cre account access

• Checks deployment access status from JWT claims (no API call)
• If access enabled: displays confirmation and next steps
• If no access: prompts user and submits request to Zendesk
• Uses CRE_ZENDESK_USERNAME and CRE_ZENDESK_PASSWORD env vars for credentials

Updated Commands

• cre whoami: Now displays Deploy Access: Enabled or Deploy Access: Not enabled (run 'cre account access' to request)
• cre workflow deploy: Checks access before deploying; prompts to request access if not enabled
• cre workflow simulate: Shows deploy access hint after successful simulation for gated users

Refactoring

• Created internal/accessrequest/ package with shared logic for access requests
• Added GetDeploymentAccessStatus() method to Credentials struct for reusable access checking
• Refactored CheckIsUngatedOrganization() to use the new method

Help Updates

• Updated cre account description to "Manage account and request deploy access"
• Added deploy access hint to global help template (shows for all commands when user is gated)