Remove `DELETE_FAST` bytecode instruction

DELETE_FAST has two uses:

1. delete var where var is a local variable
2. Cleaning up at the end of a named exception block.

A local variable can be deleted with the sequence PUSH_NULL; STORE_FAST var.

Deleting a local variable

Instead of DELETE_FAST n we can emit LOAD_FAST n; POP_TOP n; PUSH_NULL; STORE_FAST n which the bytecode optimizer will reduce to PUSH_NULL; STORE_FAST n in most cases.

Cleaning up at the end of a named exception block.

We currently emit the sequence: LOAD_CONST None; STORE_FAST n; DELETE_FAST n
which can be replaced with PUSH_NULL; STORE_FAST n

This case is far more common than explicitly deleting a local variable, so we can reduce code size as well as freeing up an opcode.

See https://github.com/faster-cpython/ideas/issues/490

Linked PRs

• gh-145983

Commencez par retracer les points d’entrée du compilateur qui émettent DELETE_FAST pour la suppression de variables locales et le nettoyage des exceptions nommées. Comparez leur sortie bytecode avec les séquences PUSH_NULL; STORE_FAST proposées, puis vérifiez que DELETE_FAST n’est plus émis et que les tests bytecode existants passent toujours ; l’issue fait référence à la PR liée gh-145983.