feat: update settings move under updates, with an interval

updates.autoCheck (was updateCheck) and updates.updateSources (was
releases) sit together with updates.autoCheckInterval, a duration (24h
by default) for how often lazysecrets looks for a newer release on its
own.

internal/ui/app/update_test.go

@@ -83,6 +83,12 @@ func TestUpdate(t *testing.T) {
 	if f2.asked != 1 {
 		t.Errorf("asked %d times a day later", f2.asked)
 	}
+	// With autoCheckInterval: 1h, two hours on is long enough.
+	mem.SetUpdateCheck(store.UpdateCheck{At: time.Now().Add(-2 * time.Hour), Tag: "v0.2.0"})
+	newDriverOpts(t, Options{Version: "0.1.1", Updater: f2.updater(), UpdateCheck: true, UpdateEvery: time.Hour, Store: mem})
+	if f2.asked != 2 {
+		t.Errorf("asked %d times, want a look after the hour", f2.asked)
+	}
 }
 
 func TestUpdateAsked(t *testing.T) {