[Issue 10014] TLS handle using MbedTLS

https://bugs.openldap.org/show_bug.cgi?id=10014

--- Comment #1 from Howard Chu hyc@openldap.org --- Thanks for the submission. I see you've got #ifdef'd support for older versions (2.x) as well as (3.x). For adding a new feature, I see no reason to support any older versions, particularly if they lack support for TLS1.3. I suggest stripping out all the 2.x support.

There are traces of copy/paste from tls_g.c and tls_o.c scattered around the file, these should be fixed.

I'd consider naming the source file "tls_mt.c" since we already had a "tls_m.c" for MozNSS in the past, and would prefer to avoid any possible confusion.