Normalize selector operation in scrollspy

[DenisLopatin]

Closes: #39198
Closes: #37858
Fix: #35566 (Hope, see below)

Description

Allows you to select the elements in the Scrollspy component that need to be escaped.

Motivation & Context

Users complain that they can't always control how their IDs for a component are filled in.

Type of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactoring (non-breaking change)
• Breaking change (fix or feature that would change existing functionality)

Checklist

• I have read the contributing guidelines
• My code follows the code style of the project (using npm run lint)
• My change introduces changes to the documentation
• I have updated the documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed

Live previews

• https://deploy-preview-41726--twbs-bootstrap.netlify.app/

Related issues

#39198
#37858
#32586
#35566 (very important)

In PR #35566, @pierresouchay added a selector search mechanism when escaping selector = selector.replaceAll(/#([^\s"#']+)/g, (match, id) => '#' + CSS.escape(id)). I removed the # symbol from there, as it interfered with the current implementation, but did not affect the previous functionality (during manual and automatic testing). I do not know why it was not necessary to escape the identifier inside the expression (#firistid#secondId is invalid), but the functionality works. In the worst case, it was necessary, but they just forgot to write the tests. At best, everything is fine.

P.S. A lot of questions, so I will be glad to receive feedback))