Collapse: make it possible to add a root or scope for where to look for triggers

Prerequisites

• I have searched for duplicate or closed feature requests
• I have read the contributing guidelines

Proposal

It would be nice if it were possible to add a root or scope that can limit where Collapse looks for elements that trigger the same target.

Something like an attribute -- perhaps data-bs-root -- with a selector, just like for data-bs-target. The Collapse constructor could then use this selector to find the root element to pass to SelectorEngine. SelectorEngine could then limit the DOM tree it searches to only the sub tree from the root element -- potentially by-passing a large part of the DOM.

HTML example

<div class="collapse-root-1">
  <button data-bs-toggle="collapse" data-bs-target=".collapse-root-1 collapse">Click me</button>
  <span class="collapse" data-bs-root=".collapse-root-1">Show me</span>
</div>
[...]
<div class="collapse-root-500">
  <button data-bs-toggle="collapse" data-bs-target=".collapse-root-500 collapse">Click me</button>
  <span class="collapse" data-bs-root=".collapse-root-500">Show me</span>
</div>

Collapse constructor proposal

class Collapse extends BaseComponent {
  constructor(element, config) {
    ...
    const root = SelectorEngine.find(element.dataset.bsRoot)
    const toggleList = SelectorEngine.find(SELECTOR_DATA_TOGGLE, root)
    ...
  }
}

Motivation and context

When you have a large DOM with many Collapse triggers, it can take multiple seconds for the Collapse constructor to iterate through all of them to find all triggers for the given Collapse target. If it were possible to limit this DOM query to a specific sub tree, it would be possible to reduce the time spent considerably.

If you have this issue today, the only way to solve it -- at least as far as I can see -- is to completely take over from Bootstrap and implement the Collapse functionality yourself. This negates the reason to use Bootstrap, so I think it would make a great addition to the library.

Start by tracing the Collapse constructor and SelectorEngine behavior described in the proposal, focusing on how triggers for a target are currently discovered. Define how a data-bs-root selector scopes those searches and how invalid or missing roots behave; done means the feature limits trigger lookup to the intended subtree without changing existing Collapse behavior.