Require signature|privileged STATUS_BAR for collapsePanels()

For apps targeting S+. This API was being exploited by malware to
prevent the user from accessing critical notifications
(go/collapse-status-bar, b/137274359).

This API was hidden and never intended to be used by 3p apps, so putting
it behind proper permission after targetSdk S. Since it's
@UnsupportedAppUsage trying to steer apps to the
Intent.ACTION_CLOSE_SYSTEM_DIALOGS (Intent.ACSD), which produces the
same effect and has been part of the API surface (as opposed to this
one). However, to fix the vulnerability (b/137274359) that intent will
be subjected to further restrictions based on privilege (who) and
circumstance (what), for more details see go/close-system-dialogs.

To lock down the abuse vector, similar restrictions to the ones applied
to Intent.ACSD will be applied to collapsePanels() NOT gated on
targetSdk, but these will be in future CLs.

Test: CTS coming
Bug: 173031413
Bug: 159105552
Bug: 137274359
Change-Id: I05f05ff6a2052820a132c2284101480448d18b77