UX: Global Variables

# Summary

Enable users to create variables and use them across the dashboard.

# Motivation

- Users may want to use some values across different applications and helm charts
- They may want to modify these values if required (Requires additional effort to modify across multiple apps)


# Proposal

https://docs.google.com/document/d/1_e7Ubmik3jROAoOMfV7Gejow_kZ_qVlRvsfKzG1820c/edit?usp=sharing
