REFACTOR: Simplify converter steps in migration tooling (#29779)

* Remove unused `report_progress_in_percent` option from step
* Remove `use_custom_progress_increment` option from the step because we can figure it out by looking at the progress
* Introduce `StepTracker` to for logging warnings and errors and tracking step progress
* Make it easier to log warnings and errors in all methods of `Step` without the need to pass around a `stats` object

migrations/lib/converters/example/steps/step3.rb

@@ -12,9 +12,11 @@ module Migrations::Converters::Example
       (1..1000).map { |i| { counter: i } }
     end
 
-    def process_item(item, stats)
+    def process_item(item)
       sleep(0.5)
 
+      step.log_warning("Test", details: item) if item[:counter] > 10 && item[:counter] < 20
+
       IntermediateDB::LogEntry.create!(type: "info", message: "Step3 - #{item[:counter]}")
     end
   end