Switch to CSS SVGs

[Anshul]

Referencing firefox-devtools/debugger#4350

We would like to switch from using react-based inline SVGs to CSS-based SVGs. The primary advantage is performance. SVGs created by React are slow to render. CSS drawn SVGs have a significant perf benefit.

TODO:

• convert Object Inspector arrows
• convert "Open in inspector" icon
• convert "Jump to definition" icon

[Nicolas Chevobbe]

Added some cases to the TODO list. Thanks @AnshulMalik for starting this