[asan] use 4Tb of address space for the asan allocator instead of 1Tb. This increases the memory available for a single size class from 16Gb to 64Gb. The total VM footprint becomes 20Tb

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@176857 91177308-0d34-0410-b5e6-96231b3b80d8