bookmark: allow disabling child provider onCurrentBookmarkChanged propagation

In `packages/modules/bookmark/src/BookmarkProvider.ts`'s constructor, child bookmark provider event subscription has:

```ts
// subscribe to child bookmark provider changes
// TODO - add support for disabling this feature
if (this._event) {
this._event.addEventListener('onCurrentBookmarkChanged', (event) => {
...
```

Add configuration support to opt out of propagating `onCurrentBookmarkChanged` events from a child bookmark provider.

Start in packages/modules/bookmark/src/BookmarkProvider.ts, focusing on the constructor and the child provider onCurrentBookmarkChanged listener. Inspect how constructor configuration is represented, then verify that propagation remains enabled by default and is skipped when the new opt-out setting is enabled.

Written by the indexing model from the issue text.