Revert "fskeyring & userspace reboot: support CE keys"

Userspace reboot turned out to be a dead end and is no longer supported.
Therefore, remove the code from vold that handled keeping CE storage
unlocked past the userdata filesystem being unmounted and mounted.

This is a revert of commit 1c6731c6 (https://r.android.com/1254615)
with various conflicts resolved.

Bug: 292469129
Change-Id: If530edaf7c1566dd3bd8b1322f935f38a2e66beb
Merged-In: If530edaf7c1566dd3bd8b1322f935f38a2e66beb
(cherry picked from commit 2b97a88b)