Reland D146570 "[scudo] Switch to use MemMap in tests"

This reverts commit 89cc5304969ded574550e0ad113f59f3d4f50303 and fix the
variable shadowing bug.

Differential Revision: https://reviews.llvm.org/D147672

GitOrigin-RevId: 755771045fc92da9b202118299884a25cd0942fc
4 files changed