Update WooPay Light and Outline button assets with new designs

[pierorocca]

Description

WooPay merchant survey feedback indicates that some merchants dislike the purple branding or that it's difficult to match the buttons to their site's brand and colors. In order to address that concern and reduce the chance of brand clash, the light purple WooPay button has been redesigned with a neutral white background.

Note: "Affects my theme appearance" is the number 2 reason merchants disable WooPay.

Acceptance criteria

1. Light button is replaced with the new Light white background button per Figma
2. Outline button is replaced with the new Outline white background button per Figma
3. The merchant settings preview correctly shows the new button for Light and Outline when selected
4. The size and call to action text functionality continues to be functional.
5. WooPay buttons on the PDP, Cart, and Checkout pages display the Light and Outline buttons when chosen in the merchant settings.

Designs

pc2DNy-42r-p2

Testing instructions

1. Open WooPay merchant settings
2. Select 'Light' button option
3. Observe preview corresponds to the Light button
4. Enable button for Product, Cart, and Checkout pages
5. Observe the Light button is displayed on the Product, Cart, and Checkout pages
6. Repeat for Outline
7. Alter the size and call to action copy in the merchant settings
8. Observe in the preview and on the product, cart and checkout pages that the size and copy matches the setting
9. In the Apple / Google Pay settings, observe that the WooPay Light and Outline buttons are rendered in the preview when selected.

[pierorocca]

cc @LCmry this would be a nice straight forward follow-up to the button work you're finishing up.