Refactor the KTLS tests to minimize code duplication.

Refactor the KTLS tests to minimize code duplication.

Use the low 4 bits of the test number directly as flags for which of
the connection sides should use KTLS or not for each test instead of
having 16 nearly identical functions to do the same thing.

This makes it easier to skip tests that aren't supported (e.g. KTLS RX
on TLS 1.3).

Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/12111)