[+] improve change_events metric processing (#932)

* [+] improve `change_events` metric processing

Move `HostState` to `RuntimeInfo.ChangeState` for better data
organization.

Convert standalone detection functions to `Reaper` methods
for consistency. Replace verbose `Info` logs with structured `Debug`
logs using `WithField()`.

Eliminate `hostState` parameter passing throughout detection methods.

Add `Total()` and `String()` helper methods to `ChangeDetectionResults`.

Improve change summary with structured logging fields instead of string
concatenation. Simplify deletion tracking by removing intermediate
arrays

* [+] add tests

Author: pashagolub