Follow up: Update FastSearch instance instead of recreating it on data change in SearchRouter

[hannojg]

This is a follow up from this PR:

• Search suffix tree implementation #48652

which was created for this issue ticket originally:

• [Performance] Typing in search is very laggy for big accounts #46591

This is a follow up task. In the PR we implemented a new tree structure to enable faster searches. Right now for every data change we create a new FastSearch instance which is quite inefficient. We want to:

• Create the FastSearch instance once, and update it on data changes
• Right now the FastSearch instance is quite disconnected from the OptionListUtils. We should see if we can consolidate the FastSearch and OptionListUtils.
  • I think it should be possible to maybe create a search tree for the whole app, which can then be used for different use cases / all the use cases OptionListUtils is serving