erp5_core: Block Folder_delete for too large selections (>1000 documents)

as an extra safety measure
3 jobs for for_testrunner_1 in 0 seconds
Status Job ID Name Coverage
  External
passed ERP5.CodingStyleTest-TestRunner1

01:36:10

passed ERP5.PerformanceTest-TestRunner1

00:22:40

failed ERP5.UnitTest-TestRunner1

02:20:12