[SIEM] [Case] Configure Cases Page

[stephmilovic]

Create a Configure Cases page that matches up with Figma prototype: https://www.figma.com/proto/r1fCnIlDvCeaS4FNgTYFxc/%5BIn-Progress%5D-Cases---MVP?node-id=41%3A345&viewport=272%2C5362%2C0.5&scaling=min-zoom

[elasticmachine]

Pinging @elastic/siem (Team:SIEM)