"Many medical procedures, including childbirth, are far more dangerous to patients, yet are not subject to ambulatory surgical-center or hospital admitting-privileges requirements. ... Given those realities, it is beyond rational belief that H. B. 2 could genuinely protect the health of women, and certain that the law 'would simply make it more difficult for them to obtain abortions.' ... When a State severely limits access to safe and legal procedures, women in desperate circumstances may resort to unlicensed rogue practitioners. ... [L]aws like H. B. 2 that 'do little or nothing for health, but rather strew impediments to abortion' cannot survive judicial inspection."