Revert "[scudo] Store more blocks in each TransferBatch" (#83078)

Reverts llvm/llvm-project#70390

There's a bug caught by
`ScudoCombinedTestReallocateInPlaceStress_DefaultConfig.ReallocateInPlaceStress`
with gwp asan. It's an easy fix but given that this is a major change, I
would like to revert it first