[NFC][Asan] Reorder bitfields

[vitalybuka]

Summary

Depends on D87644.

[morehouse]

LGTM

compiler-rt/lib/asan/asan_allocator.cpp

 class ChunkHeader {
  public:
   atomic_uint8_t chunk_state;
   u8 alloc_type : 2;
   u8 lsan_tag : 2;
 
   // align < 8 -> 0
   // else      -> log2(min(align, 512)) - 2
-  u16 user_requested_alignment_log : 3;
+  u8 user_requested_alignment_log : 3;
 
  private:
-  u16 user_requested_size_hi : 13;
+  u16 user_requested_size_hi;
   u32 user_requested_size_lo;
   atomic_uint64_t alloc_context_id;
 
  public:
   uptr UsedSize() const {
     uptr R = user_requested_size_lo;
     if (sizeof(uptr) > sizeof(user_requested_size_lo))
       R += (uptr)user_requested_size_hi << (8 * sizeof(user_requested_size_lo));