feat(accordion): add default styles for ionic theme (#29933)

- Updates Accordion to use the Ionic theme styles defined in Figma
- Adds an e2e test to the basic test to check for text content in the `content` slot
- Adds the `ionic` theme to the `multiple` e2e test
- Adds an e2e test for `states` which screenshots disabled, activated & focused
- Updates Item to accommodate the Accordion styles
- Updates the global core scss file to override the Toggle Icon and Items in an Accordion

Author: brandyscarney