Re-evaluate the concept of preloding routes

Problem/Motivation

#3503843: Remove automatic preloading of all "public" routes, cache routes in fast chained bin considerably changes how we preload routes, it basically removes the bulk preload and the concept of preloading still-serialized route definitions. We considered removing it entirely and just relying on getRouteByNames which exactly the same logic now.

The one thing that might still keep it useful is the changing it to just record which routes should be preloaded and allow multiple calls before the actual calls happen (for example from multiple menu blocks), so we can combine them. The idea is similar to support for preloading cache tags.

If this doesn't work out/is not beneficial enough, we can deprecate the interface.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet