Zeroize intermediate secrets in unlockLskfBasedProtector()

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

Zeroize stretchedLskf, weaverKey, gkPassword, and protectorSecret.

Bug: 320392352
Test: atest FrameworksServicesTests:com.android.server.locksettings
Flag: EXEMPT bugfix
Change-Id: I4a6c5bae60d4ef540d68bdec350edc328512e0c9