[memprof] Switch allocator to dynamic base address (llvm#98510)

memprof_rtl.cpp calls InitializeShadowMemory() - which
dynamically/"randomly" chooses a base address for the shadow mapping -
prior to InitializeAllocator(). If we are unlucky, the shadow memory may
be mapped in the same region where the allocator wants to be.

This patch fixes the issue by changing the allocator to dynamically
choosing a base address, as suggested by Vitaly. For comparison, HWASan
already dynamically chooses the base addresses for the shadow mapping
and allocator.

The "unlucky" failure was observed on a new buildbot:
https://lab.llvm.org/buildbot/#/builders/66/builds/1361/steps/17/logs/stdio

---------

Co-authored-by: Vitaly Buka <vitalybuka@gmail.com>

compiler-rt/lib/memprof/memprof_allocator.h

@@ -46,11 +46,7 @@ struct MemprofMapUnmapCallback {
   void OnUnmap(uptr p, uptr size) const;
 };
 
-#if SANITIZER_APPLE
-constexpr uptr kAllocatorSpace = 0x600000000000ULL;
-#else
-constexpr uptr kAllocatorSpace = 0x500000000000ULL;
-#endif
+constexpr uptr kAllocatorSpace = ~(uptr)0;
 constexpr uptr kAllocatorSize = 0x40000000000ULL; // 4T.
 typedef DefaultSizeClassMap SizeClassMap;
 template <typename AddressSpaceViewTy>