Zeroize CE storage key in setCeStorageProtection()

Secrets derived from or unlocked by the LSKF need to be zeroized as soon
as they are no longer needed.

Bug: 320392352
Test: atest FrameworksServicesTests:com.android.server.locksettings
Flag: EXEMPT bugfix
Change-Id: Ic2b0b22051f91fd8a9eff96ca2156fd379ef5c96