Revert^2 "Cryptographic security for MAX_BOOT_LEVEL"

Revert submission revert-1660531-max-boot-level-crypto-KFMCEDKSIV

Reason for revert: topic:vold-use-keystore2 has landed fixing the bug

Reverted changes:
Ibf63734a: Revert "Set earlyBootEnded before apex starts"
Id02f63a7: Revert "Expose AID_KEYSTORE"
Ibcedeff4: Revert "Cryptographic security for MAX_BOOT_LEVEL"

Restored changes:
Ia3b968afc:Set earlyBootEnded before apex starts
Ia69891291:Expose AID_KEYSTORE
I12530cd13:Cryptographic security for MAX_BOOT_LEVEL

Reverted-SHA1: 229f2c038c22ee271e06c1f919e2632fa014bc19

Original commit message:
Use a KDF to generate a key for each boot level, anchored in a key
which can only be used once per boot.

Bug: 176450483
Test: atest com.android.tests.odsign.OnDeviceSigningHostTest#verifyArtUpgradeSignsFiles
Change-Id: I62609052647316c5c381e1df12963996aba97f23
diff --git a/keystore2/src/lib.rs b/keystore2/src/lib.rs
index 62dc16a..0916af1 100644
--- a/keystore2/src/lib.rs
+++ b/keystore2/src/lib.rs
@@ -18,6 +18,7 @@
 pub mod apc;
 pub mod async_task;
 pub mod authorization;
+pub mod boot_level_keys;
 pub mod database;
 pub mod ec_crypto;
 pub mod enforcements;