Add the ability to do client side tracing in quictestlib.c

Add the ability to do client side tracing in quictestlib.c

We add a new flag QTEST_FLAG_CLIENT_TRACE to get debug tracing output if
required.

Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/22157)