[Sanitizer] Make GetBlockBeginFastLocked parameters const.

compiler-rt/lib/sanitizer_common/sanitizer_allocator_combined.h

public:
   void *GetBlockBegin(const void *p) {
     if (primary_.PointerIsMine(p))
       return primary_.GetBlockBegin(p);
     return secondary_.GetBlockBegin(p);
   }
 
   // This function does the same as GetBlockBegin, but is much faster.
   // Must be called with the allocator locked.
-  void *GetBlockBeginFastLocked(void *p) {
+  void *GetBlockBeginFastLocked(const void *p) {
     if (primary_.PointerIsMine(p))
       return primary_.GetBlockBegin(p);
     return secondary_.GetBlockBeginFastLocked(p);
   }
 
   uptr GetActuallyAllocatedSize(void *p) {
     if (primary_.PointerIsMine(p))
       return primary_.GetActuallyAllocatedSize(p);

compiler-rt/lib/sanitizer_common/sanitizer_allocator_secondary.h

void EnsureSortedChunks() {
     Sort(reinterpret_cast<uptr *>(chunks), n_chunks_);
     for (uptr i = 0; i < n_chunks_; i++)
       AddressSpaceView::LoadWritable(chunks[i])->chunk_idx = i;
     chunks_sorted_ = true;
   }
 
   // This function does the same as GetBlockBegin, but is much faster.
   // Must be called with the allocator locked.
-  void *GetBlockBeginFastLocked(void *ptr) {
+  void *GetBlockBeginFastLocked(const void *ptr) {
     mutex_.CheckLocked();
     uptr p = reinterpret_cast<uptr>(ptr);
     uptr n = n_chunks_;
     if (!n) return nullptr;
     EnsureSortedChunks();
     Header *const *chunks = AddressSpaceView::Load(chunks_, n_chunks_);
     auto min_mmap_ = reinterpret_cast<uptr>(chunks[0]);
     auto max_mmap_ = reinterpret_cast<uptr>(chunks[n - 1]) +