gh-157468: Validate correct builtins used under JIT

[johng]

This adds the two checks at tracing and at JIT runtime that the builtin dict is the original interpreter's builtins

• Issue: Tier 2 optimizer may use canonical builtins for functions with a copied __builtins__ dictionary #157468

[cocolato]

Please don't force push PRs. We‘ll squash merge commits at the end. And some comments:

[cocolato]

I don't think we need a new helper here. We can keep the original convert_global_to_const(), check for two free slots before calling it, then emit the guard and converted instruction with ADD_OP.

[cocolato]

This would remove the nested capacity branch and the assignment back to NULL:

Suggested change

	if (ctx->frame->globals_checked_version != 0 && ctx->frame->globals_watched) {
	cnst = convert_global_to_const(this_instr, builtins);
	cnst = lookup_global_const(this_instr, builtins);
	if (cnst != NULL) {
	/* Emitting two uops in place of one: make sure they fit. */
	if (uop_buffer_remaining_space(&ctx->out_buffer) < 2) {
	cnst = NULL;
	}
	else {
	ADD_OP(_GUARD_BUILTINS_IS_CANONICAL, 0, 0);
	ADD_OP(_Py_IsImmortal(cnst) ? _LOAD_CONST_INLINE_BORROW
	: _LOAD_CONST_INLINE,
	0, (uintptr_t)cnst);
	}
	}
	}
	if (ctx->frame->globals_checked_version != 0 &&
	ctx->frame->globals_watched &&
	uop_buffer_remaining_space(&ctx->out_buffer) >= 2)
	{
	cnst = convert_global_to_const(this_instr, builtins);
	if (cnst != NULL) {
	ADD_OP(_GUARD_BUILTINS_IS_CANONICAL, 0, 0);
	ADD_OP(this_instr->opcode, 0, this_instr->operand0);
	}
	}