BLI: use no_unique_address attribute

Even though the `no_unique_address` attribute has only been standardized
in C++20, compilers seem to support it with C++17 already. This attribute
allows reducing the memory footprint of structs which have empty types as
data members (usually that is an allocator or inline buffer in Blender).
Previously, one had to use the empty base optimization to achieve the same
effect, which requires a lot of boilerplate code.

The types that benefit from this the most are `Vector` and `Array`, which
usually become 8 bytes smaller. All types which use these core data structures
get smaller as well of course.

Differential Revision: https://developer.blender.org/D14993

source/blender/blenlib/BLI_stack.hh

@@ -96,7 +96,7 @@ class Stack {
   int64_t size_;
 
   /** The buffer used to implement small object optimization. */
-  TypedBuffer<T, InlineBufferCapacity> inline_buffer_;
+  BLI_NO_UNIQUE_ADDRESS TypedBuffer<T, InlineBufferCapacity> inline_buffer_;
 
   /**
    * A chunk referencing the inline buffer. This is always the bottom-most chunk.
@@ -105,7 +105,7 @@ class Stack {
   Chunk inline_chunk_;
 
   /** Used for allocations when the inline buffer is not large enough. */
-  Allocator allocator_;
+  BLI_NO_UNIQUE_ADDRESS Allocator allocator_;
 
  public:
   /**