[apex] Fix parsing of triggers with declarations

Only the grandchildren of a trigger block were ending up in the tree,
but the direct children of triggerBlock were missing, e.g.
ForLoopStatement. This caused OperationWithHighCostInLoop to not
find the loop anymore in triggers.

This will probably fix other false negatives in triggers in
other rules as well.

Fixes #5139

docs/pages/release_notes.md

@@ -15,6 +15,8 @@ This is a {{ site.pmd.release_type }} release.
 ### 🚀 New and noteworthy
 
 ### 🐛 Fixed Issues
+* apex-performance
+  * [#5139](https://github.com/pmd/pmd/issues/5139): \[apex] OperationWithHighCostInLoop not firing in triggers
 * plsql-bestpractices
   * [#5132](https://github.com/pmd/pmd/issues/5132): \[plsql] TomKytesDespair - exception for more complex exception handler