SSL connection metadata should be available to request filters

## What is the problem your feature solves, or the need it fulfills?

SSL connection metadata should be available to filters such as request_filter.

Metadata such as the following would be useful for routing, logging, and generation of JA3 fingerprints

- SNI
- Cipher
- TLS Version
- Extensions list
- Client ciphers, curve list and formats

## Describe the solution you'd like

The metadata would be accessible through via the request_filters through the `Session` struct.

## Describe alternatives you've considered

There are no alternatives as the data is not currently available.

## Additional context

HAProxy provides the following SSL metadata:
https://www.haproxy.com/documentation/haproxy-configuration-manual/latest/#7.3.4-ssl_fc

NGINX:
http://nginx.org/en/docs/http/ngx_http_ssl_module.html#variables