Fix Cart & Checkout sidebar layout broken in some themes

[Aljullu]

Cart and Checkout blocks were not playing well with themes that didn't define box-sizing: border-box; for all elements. I discovered that while investigating #3110, but it has been for some time in my todo list, so I decided to create a PR directly.

Screenshots

Before:

After:

How to test the changes in this Pull Request:

1. Install and activate Artisan or Threads theme.
2. Go to the Cart or Checkout blocks and verify the sidebar is shown on the right instead of below.
3. Switch back to Storefront or Twenty Twenty and verify there are no regressions.

Changelog

Fixed a style conflict that was affecting some themes and was breaking their sidebar layout in the Cart and Checkout blocks.

[github-actions]

Size Change: +5 B (0%)

Total Size: 1.11 MB

Filename	Size	Change
build/style-rtl.css	18 kB	+2 B (0%)
build/style.css	18 kB	+3 B (0%)

ℹ️ View Unchanged

Filename	Size	Change
build/active-filters-frontend.js	8.78 kB	0 B
build/active-filters.js	8.85 kB	0 B
build/all-products-frontend.js	31.2 kB	0 B
build/all-products.js	35.7 kB	0 B
build/all-reviews.js	9.79 kB	0 B
build/atomic-block-components/add-to-cart-frontend.js	8.89 kB	0 B
build/atomic-block-components/add-to-cart.js	7.46 kB	0 B
build/atomic-block-components/add-to-cart~atomic-block-components/button.js	3.16 kB	0 B
build/atomic-block-components/add-to-cart~atomic-block-components/image~atomic-block-components/title.js	335 B	0 B
build/atomic-block-components/button-frontend.js	2.02 kB	0 B
build/atomic-block-components/button.js	835 B	0 B
build/atomic-block-components/category-list-frontend.js	469 B	0 B
build/atomic-block-components/category-list.js	475 B	0 B
build/atomic-block-components/image-frontend.js	1.71 kB	0 B
build/atomic-block-components/image.js	1.15 kB	0 B
build/atomic-block-components/price-frontend.js	2.1 kB	0 B
build/atomic-block-components/price.js	2.13 kB	0 B
build/atomic-block-components/rating-frontend.js	524 B	0 B
build/atomic-block-components/rating.js	527 B	0 B
build/atomic-block-components/sale-badge-frontend.js	863 B	0 B
build/atomic-block-components/sale-badge.js	865 B	0 B
build/atomic-block-components/sku-frontend.js	389 B	0 B
build/atomic-block-components/sku.js	394 B	0 B
build/atomic-block-components/stock-indicator-frontend.js	568 B	0 B
build/atomic-block-components/stock-indicator.js	571 B	0 B
build/atomic-block-components/summary-frontend.js	918 B	0 B
build/atomic-block-components/summary.js	925 B	0 B
build/atomic-block-components/tag-list-frontend.js	466 B	0 B
build/atomic-block-components/tag-list.js	472 B	0 B
build/atomic-block-components/title-frontend.js	1.23 kB	0 B
build/atomic-block-components/title.js	1.06 kB	0 B
build/attribute-filter-frontend.js	18.1 kB	0 B
build/attribute-filter.js	12.4 kB	0 B
build/blocks.js	3.54 kB	0 B
build/cart-frontend.js	69 kB	0 B
build/cart.js	37.4 kB	0 B
build/checkout-frontend.js	84.2 kB	0 B
build/checkout.js	40.8 kB	0 B
build/editor-rtl.css	13.9 kB	0 B
build/editor.css	13.9 kB	0 B
build/featured-category.js	7.72 kB	0 B
build/featured-product.js	9.97 kB	0 B
build/handpicked-products.js	7.37 kB	0 B
build/price-filter-frontend.js	14.4 kB	0 B
build/price-filter.js	10.3 kB	0 B
build/product-best-sellers.js	7.44 kB	0 B
build/product-categories.js	3.23 kB	0 B
build/product-category.js	8.38 kB	0 B
build/product-new.js	7.6 kB	0 B
build/product-on-sale.js	7.99 kB	0 B
build/product-search.js	3.56 kB	0 B
build/product-tag.js	6.52 kB	0 B
build/product-top-rated.js	7.57 kB	0 B
build/products-by-attribute.js	8.31 kB	0 B
build/reviews-by-category.js	11.8 kB	0 B
build/reviews-by-product.js	13.4 kB	0 B
build/reviews-frontend.js	9.37 kB	0 B
build/single-product-frontend.js	34 kB	0 B
build/single-product.js	10.1 kB	0 B
build/vendors-style-rtl.css	1.03 kB	0 B
build/vendors-style.css	1.03 kB	0 B
build/vendors.js	416 kB	0 B
build/vendors~atomic-block-components/price-frontend.js	5.65 kB	0 B
build/wc-blocks-data.js	7.09 kB	0 B
build/wc-blocks-middleware.js	931 B	0 B
build/wc-blocks-registry.js	2.28 kB	0 B
build/wc-payment-method-bacs.js	790 B	0 B
build/wc-payment-method-cheque.js	787 B	0 B
build/wc-payment-method-cod.js	875 B	0 B
build/wc-payment-method-paypal.js	831 B	0 B
build/wc-payment-method-stripe.js	11.9 kB	0 B
build/wc-settings.js	2.33 kB	0 B
build/wc-shared-context.js	1.53 kB	0 B
build/wc-shared-hocs.js	1.66 kB	0 B

_{compressed-size-action}

[senadir]

Can confirm that it fixes that issue.