Allow raw tls_options to be passed through to gen_smtp

[arjan]

Since OTP 26, TLS checking has changed a bit. For gen_smtp it is now necessary (see this ticket) to pass in the tls_options which are retrieved from the :tls_certificate_check erlang module:

 tls_options: :tls_certificate_check.options(relay)

This patch allows the :tls_options configuration key to be passed through as-is to gen_smtp.

[nclark]

Is there a current recommendation for users of bamboo_smtp 4.2.2? I'm troubleshooting an application that stopped sending mail after upgrading to OTP26 with the {:error, {:temporary_failure, ~c"52.192.253.213", :tls_failed}} type of error. It seems like the only thing that works is tls_verify: :verify_none which is not ideal.