* fix(scrollspy): Handle nested navs when nav-link inside nav-item

* [scrolspy] Find only child .nav-link's inside .nav-item

* [scrollspyt] Add tests for nested navs with nav-link inside nav-item

* fix troy-o's in test

* Replace element.offet* by getBoundingClientRect()

* Use variable to store BoundingClientRect

* Fix cc issue...

* fix wrong activation of all nested links;
just first level item should be activated

* use template instead of string concatenation

When the rubberband effect causes Safari to scroll past the top of the
page, the value of scrollTop becomes negative. If the offset of the first
ScrollSpy target is 0 - essentially if the target is at the top of the
page - then ScrollSpy should not clear the active item. Conceptually, the
first item should remain active when rubberbanding past the top of the
page.

This commit fixes issue #21055 by verifying the first scrollspy target is
not at the top of the page before clearing the active nav-item.

Fixes #19028

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Errata from:
* 8ce5da30
* 5d3144e8
which missed a few numbers.

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