Rename split-loop-with-lambda to slice-with-lambda

The refactoring is now published as Slice on sammancoaching.org:
https://sammancoaching.org/refactorings/slice.html

- git mv ideas/split-loop-with-lambda -> ideas/slice-with-lambda
- rename learning-hour file and update frontmatter name
- update paths in tools/rehearse scripts and report title
- update prose: 'Split Loop with Lambda' -> 'Slice with Lambda'
  in learning hour, exercise READMEs, storyboard, solution comments
- link the published Slice refactoring from the pattern draft

ideas/slice-with-lambda/exercise/rehearsal-runs/B/verify.txt

@@ -0,0 +1,10 @@
+--- Run B ---
+final diff vs pristine: 54 changed lines -> /tmp/rehearsal/runs/B/diff.patch
+mvn test with solution's test + approved file:
+  RESULT: PASS (deterministic)
+structural checks:
+  [x] method collectExpectedWeather exists
+  [x] takes LongFunction<Boolean> parameter
+  [i] note: 'scorer' still referenced in LongRangeForecasts.java
+  [x] lambda syntax present
+  [i] main class differs from reference solution (may still be a valid variant)