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

Inizia tracciando i punti di ingresso del compilatore che emettono DELETE_FAST per l’eliminazione delle variabili locali e la pulizia delle eccezioni denominate. Confronta il loro output del bytecode con le sequenze PUSH_NULL; STORE_FAST proposte, quindi verifica che DELETE_FAST non venga più emesso e che i test del bytecode esistenti continuino a passare; l’issue fa riferimento alla PR collegata gh-145983.