* peterdmv/ssl/fix-handshake-hello/ERL-975/OTP-15888:
  ssl: Fix negative tests in ssl_basic_SUITE
  ssl: Fix run_client_error/1 in ssl_test_lib
  ssl: Fix ssl_handshake:extension_value/1

* peterdmv/ssl/tls12-java11-interop/ERL-973/OTP-15887:
  ssl: Add interop test
  ssl: Improve handling of signature algorithms

* ingela/ssl/handshake-handling/ERL-968/OTP-15879:
  ssl: Correct handshake handling

Handle new TLS 1.2/1.3 extensions.

TLS 1.2 ClientHello caused handshake failure in the TLS 1.2 server
if the signature_algorithms_cert extension contained legacy algorithms.

Update TLS 1.2 server to properly handle legacy signature algorithms
in the signature_algorithms_cert extension.

Update TLS 1.3 client so that it can send legacy algorithms in its
signature_algorithms_cert extension.

Solves ERL-968, a refactoring bug could cause part of a server key exchange message to
be appended, to an incorrectly duplicated, certificate handshake message. In the end
causing an ASN1 decoding error. That in turn did not end up the correct error handling branch.

* ingela/ssl/dtls-multiplxor/ERL-962/OTP-15864:
  ssl: Add missing gen_server return value in DTLS packet demux process

* ingela/ssl/ret-ext/ERL-951/OTP-15862:
  ssl: Fix broken return value