Tracker #29939: Improve setting definition DSL and move setting registry to memory
Load Setting index page from memory registry
Implement simple search_for() on the memory registry, so we can mimic the Setting model behaviour and serve the Setting index page from memory.
Fixes #32287 - setting index loads from registry
The values provided on the Setting index page are now served from
registry, with simple search API, that can be easily improve to support
more querying features.