[Woo POS] Update UI for card reader connection modals

[joshheald]

Improvements to the design of the card reader connection screens, shown in a modal during reader connection.

• [x] New image for errors (requested: p1724660697349469-slack-C0354HSNUJH)
• [x] New image for low battery errors (requested: p1724660697349469-slack-C0354HSNUJH)
• [x] #13691
• [x] Use POS button styles
• [x] Ensure modal is correct size
• [x] Change title/subtitle of Found reader
• [x] Replace cancel button with x-mark
• [x] Move all text below images
• [ ] ~Spacer between text and buttons~
• [x] Scroll where required
• [x] Update multiple readers view to have sensible background etc

Designs: TfaZ4LUkEwEGrxfnEFzvJj-fi-4354_119342