Code listing style fixes, remove extra line management

[dobromir-hristov]

closes #662

rdar://109756906

Summary

This PR refactors the css styling of the CodeListing in order to properly render new lines coming from code.

Dependencies

• This builds upon Fix extra empty line issue on tutorial #663
• probably fixes Fix issues with new lines not rendering, when multiline blocks are used #502 properly

Testing

This PR should be tested with as many examples as possible, across Tutorials and Doc pages.

We should test with scrollable content, multi-line content, and any combination of them.

Checklist

Make sure you check off the following items. If they cannot be completed, provide a reason.

• Added tests - css mostly
• Ran npm test, and it succeeded
• Updated documentation if necessary

[dobromir-hristov]

@Kyle-Ye give this a try and let me know :)

[Kyle-Ye]

@Kyle-Ye give this a try and let me know :)

Tried it. It seems to fix all the bug I know. Thanks

• Missing new line in multi string swift code
• Extra new line in tutorial
• Proper new line copy behavior in tutorial.

[Kyle-Ye]

LGTM

[dobromir-hristov]

@swift-ci test

[mportiz08]

Nice work!

Looks like this fixes both the tutorial and multiple line literal issue, and I also wasn't able to find any obvious regressions with any other complicated code listing we might render, like API Changes, collapsible REST code listings, etc

🚀

[marinaaisa]

Tested and seems to look good now 💯

[dobromir-hristov]

@swift-ci test