ISSUE-2793: TLS Hostname verification undefined for C++/python client

[sijie]

Original Issue: apache#2793

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I've not tested with code, but it looks like TLS hostname verification is a mess for the C++ client (and python by extension).

For binary connections, no hostname verification takes place as far as I can see. For http connections (for lookups) it takes place every time.

I suspect this made it through testing since the tls certs used to test C++ use localhost as the common name. We should expose the ability to add the host verification in the configuration.

[Huanli-Meng]

need a host verification code example through python client.

[Huanli-Meng]

Doc is updated, here is the doc PR: apache#7162

update the docs for the following releases: 2.5.2---2.2.0: apache#7182

[Huanli-Meng]

Docs for Pulsar releases: master--2.2.0 are merged. I think this issue can be closed.