Consider JetBrains Mono for Modern UI typography and density

Is your feature request related to a problem? Please describe.
With the new Modern UI ([#334285](https://github.com/microsoft/vscode/issues/334285)), density and screen space utilization have become major concerns, especially on smaller displays. Standard fonts can sometimes require larger line heights to remain readable, contributing to the extra vertical and horizontal spacing.

Describe the solution you'd like
Consider evaluating or referencing JetBrains Mono for Modern UI typography elements. JetBrains Mono is specifically designed for developers and compact UI spaces. It provides:

- High legibility at smaller font sizes.

- Efficient vertical line-height spacing.

- Clear character distinction which helps maintain density without reducing readability.

Describe alternatives you've considered
Using Compact Mode (window.density.layout: compact), but optimizing the font layer itself could provide a better visual hierarchy natively.