[compiler-rt] [scudo] Add primary option to zero block on dealloc. (PR #142394)

[via llvm-commits]

https://github.com/ChiaHungDuan commented:

Given that we have the threshold, this is not specific to the primary allocator. It's better to make this as a top level config and implement it in combined.h

https://github.com/llvm/llvm-project/pull/142394