[JVMCI] handle non-cloneable SHA-1 MessageDigest implementation

jdk.vm.ci.hotspot.HotSpotSpeculationEncoding incorrectly assumes that all MessageDisgest implementations of the SHA-1 algorithm are cloneable. This is not always true. Solaris has a MessageDigest SHA-1 implementation[1] that is not cloneable. Even if Solaris/SPARC support is dropped, this should still be addressed in case a SHA-1 MessageDigest implementation is introduced that is not cloneable.

[1] https://github.com/openjdk/jdk/blob/6bab0f539fba8fb441697846347597b4a0ade428/src/jdk.crypto.ucrypto/solaris/classes/com/oracle/security/ucrypto/NativeDigest.java#L241