Do not register Curve25519 as a key factory directly

Do not register Curve 25519 algorithms as key factories, until we fix
the registration to be in compliance with JEP 324.

Bug: 222440855
Bug: 222194540
Test: atest android.keystore.cts.Curve25519Test android.keystore.cts.KeyFactoryTest#testAlgorithmList CtsLibcoreTestCases:libcore.java.security.ProviderTest#test_Provider_getServices
Merged-In: Ibd53070a890955affaff5e4e7213892afd423db7
Change-Id: I11b3574aeff54b3eb8bf496c4c14aa1338629ce5