When he announced his intention yesterday to name Sandra O’Connor to the U.S. Supreme Court, President Reagan seems to have fulfilled not one but both of his long-standing commitments on the subject. First , of course , he had promised to search for a qualified woman to fill a vacancy ; not surprisingly, it appears he has easily found one. But second, it looks like the nominee meets the ideological test Mr. Reagan said he would apply-not the test of political conservatism , but the test of belief in a philosophy of judicial restraint. Mr. Reagan is fed up with the imperial judiciary . So are a lot of people . So is the Supreme Court itself . The question is whether they are fed up for the right reasons . About five years ago commentators began to notice that a new kind of judicial activism was abroad in the land . It involved a certain role reversal: The traditionally conservative courts seemed now to be fighting the Executive and Legislature in behalf of the liberal principle of extending government’s protective scope. Moreover , the new activism seemed on its way to becoming entrenched so that it could not be easily reversed by elections or swings of opinion. The courts were operating by expanding the definitions of basic constitutional concepts like standing and due process; such ground once broken is difficult to abandon. The courts also had a seemingly ever-growing field of overall government activity and public interest lawyers to cope with ; this , too, seemed a near irreversib