refactor: Creates the VizType enum

[michael-s-molina]

SUMMARY

This PR creates a new enum for the visualization types and reference it throughout the code. The objective is to keep a centralized place for our definitions and avoid text references that are error prone.

TESTING INSTRUCTIONS

CI should be sufficient.

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[giftig]

Nice, looks like a good improvement.