Revamp Scrollspy using Intersection observer (#33421)

* Revamp scrollspy to use IntersectionObserver

* Add smooth scroll support

* Update scrollspy.js/md

* move functionality to method

* Update scrollspy.js

* Add SmoothScroll to docs example

* Refactor Using `Maps` and smaller methods

* Update scrollspy.md/js

* Update scrollspy.spec.js

* Support backwards compatibility

* minor optimizations

* Merge activation functionality

* Update scrollspy.md

* Update scrollspy.js

* Rewording some of the documentation changes

* Update scrollspy.js

* Update scrollspy.md

* tweaking calculation functionality & drop text that suggests, to deactivate target when wrapper is not visible

* tweak calculation

* Fix lint

* Support scrollspy in body & tests

* change doc example to a more valid solution

Co-authored-by: XhmikosR <xhmikosr@gmail.com>
Co-authored-by: Patrick H. Lauke <redux@splintered.co.uk>

js/src/dom/manipulator.js

@@ -57,22 +57,6 @@ const Manipulator = {
 
   getDataAttribute(element, key) {
     return normalizeData(element.getAttribute(`data-bs-${normalizeDataKey(key)}`))
-  },
-
-  offset(element) {
-    const rect = element.getBoundingClientRect()
-
-    return {
-      top: rect.top + window.pageYOffset,
-      left: rect.left + window.pageXOffset
-    }
-  },
-
-  position(element) {
-    return {
-      top: element.offsetTop,
-      left: element.offsetLeft
-    }
   }
 }