gh-145858: Remove DELETE_DEREF bytecode instruction

Replace DELETE_DEREF with the sequence LOAD_DEREF + POP_TOP + PUSH_NULL + STORE_DEREF in the compiler. Adapt STORE_DEREF to handle NULL stackref for cell clearing.

Author: aleksandr.tseluyko

Doc/library/dis.rst

@@ -1547,17 +1547,6 @@ iterations of the loop.
       ``i`` is no longer offset by the length of :attr:`~codeobject.co_varnames`.
 
 
-.. opcode:: DELETE_DEREF (i)
-
-   Empties the cell contained in slot ``i`` of the "fast locals" storage.
-   Used by the :keyword:`del` statement.
-
-   .. versionadded:: 3.2
-
-   .. versionchanged:: 3.11
-      ``i`` is no longer offset by the length of :attr:`~codeobject.co_varnames`.
-
-
 .. opcode:: COPY_FREE_VARS (n)
 
    Copies the ``n`` :term:`free (closure) variables <closure variable>` from the closure

Include/internal/pycore_magic_number.h

@@ -294,6 +294,7 @@ Known values:
     Python 3.15a4 3661 (Lazy imports IMPORT_NAME opcode changes)
     Python 3.15a8 3662 (Add counter to RESUME)
     Python 3.15a8 3663 (Merge GET_ITER and GET_YIELD_FROM_ITER. Modify SEND to make it a bit more like FOR_ITER)
+    Python 3.15a8 3664 (Remove DELETE_DEREF opcode)
 
 
     Python 3.16 will start with 3700
@@ -307,7 +308,7 @@ PC/launcher.c must also be updated.
 
 */
 
-#define PYC_MAGIC_NUMBER 3663
+#define PYC_MAGIC_NUMBER 3664
 /* This is equivalent to converting PYC_MAGIC_NUMBER to 2 bytes
    (little-endian) and then appending b'\r\n'. */
 #define PYC_MAGIC_NUMBER_TOKEN \