LDAP: Review, testing and update of LDAP TLS CA cert control
Review of #4913
Added testing to cover option.
Updated option so it can be used for a CA directory, or a CA file.
Updated option name to be somewhat abstracted from original underling
PHP option.
Tested against Jumpcloud.
Testing took hours due to instability which was due to these settings
sticking and being unstable on change until php process restart.
Also due to little documentation for these options.
X_TLS_CACERTDIR option needs cert files to be named via specific hashes
which can be achieved via c_rehash utility.
This also adds detail on STARTTLS failure, which took a long time to
discover due to little detail out there for deeper PHP LDAP debugging.