Prepare for converting stylesheets/pages/projects.scss into page specific bundle

What does this MR do?

The current project.scss file has weak scoped style rules making it difficult to simply move to a separate file and only include on specific pages. In an attempt to reduce the file size, and in helping make it easier to eventually move to a page specific bundle, I am converting style rule properties to utility classes and removing old obsolete style rules.

Pleaes take note:

1. Some style properties were in contravention of GitLab's design system and in such cases the nearest matching utility classes matching the existing values were used.
2. Even though some style rules might have completely been removed from the projects.scss file, the class is sometimes left in the markup due to tests or JavaScript relying on it. Where there were no other references it was removed from the markup.

Each commit in this MR represents a small refactoring.

Depends on gitlab-ui!1775 (diffs)

How to test

You should be able to run this branch locally and compare it to the project pages on gitlab.com and there should be no difference.

gitlab.com	local

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Related to #239865 (closed)