[8u] TLSv1.3 RFR: 8245470: Fix JDK8 compatibility issues

[Alexey Bakhtin]

Please review changes required to backport TLSv1.3 protocol from JDK11.0.7 to JDK8u

This is the forth part of backport discussed in the thread [1]

JBS task: https://bugs.openjdk.java.net/browse/JDK-8245470
Webrev: http://cr.openjdk.java.net/~abakhtin/tls1.3/8245466/8245470/webrev.v0/

This patch fixes common build issues caused by changes related to using a class from another package or different language constructions.
Also, this patch includes changes in the HandshakeHash class caused by the absence of MessageDigestSpi2 interface in JDK8

The patch should be applied after the patch for JDK-8245469

[1] - https://mail.openjdk.java.net/pipermail/jdk8u-dev/2020-May/011664.html

Regards
Alexey