Allow providing TlsCertificates when creating a redis Manager

[rtimush]

This PR makes it possible to use TLS with deadpool_redis by providing the TlsCertificates instance when creating a Manager.

An alternative would be to make it possible to create a Manager directly from a Client. However, to me it looks like providing the TlsCertificates aligns better with what other deadpool crates do.

The original issue (#404) also suggests that deadpool_redis::Config could have a tls_params field. This appears to be tricky, as the TlsConnParams struct is not exposed directly by the redis crate.

Closes #404.