Full-width paragraphs may have wrong width when not in the Content region

[bberndt-uaz]

Describe the bug

Pull request #3774 updated the styling of full-width paragraphs to apply to all regions, not just the Content region:

• Closes #3773 Styling issues with Box style Text on Media paragraphs #3774

However, although this resolved the issue for Text on Media paragraphs in certain regions (like Content Top), it introduced an additional bug where full-width Text with Background or Text on Media paragraphs can have the incorrect width in regions other than Content:

This problem occurs due to this CSS rule being incorrectly applied to full-width paragraphs which are not in the Content region:

.region .full-width-background {
    margin-left: var(--full-width-left-distance);
    margin-right: var(--full-width-right-distance);
    overflow: hidden;
}

The CSS variables above are calculated specifically for the Content region and should not be used in relation to other regions.

To Reproduce

Steps to reproduce the behavior:

1. Create a flexible block with a full-width Text with Background paragraph.
2. In Block Layout, add the block to a region such as Full width content bottom or Content bottom.
3. Observe that the Text with Background paragraph is not full-width: there is a large margin on the right side.

Proposed resolution

Revert one or more of the changes from #3774 and update CSS as needed to fix remaining issues specific to Text with Background paragraphs.

Expected behavior

Paragraphs with the "Full width" checkbox checked should use the full width of the page.