allow passing in TLS connector

[Be-ing]

This is #609 rebased on the current main branch. The dependency updates have been split to #754.

From the original PR:

We've been through a number of different possible rustls connectors, and we're currently using one (rustls-platform-verifier) that doesn't have feature flags in livekit or tungstenite yet.

Instead of requiring that every transitive dependency supports the rustls feature flags we need, it's much easier to pass only the __rustls-tls feature flag and pass the Connector that we create with our configuration down the stack.

[ladvoc]

Hi @Be-ing, thank you for your contribution—this will resolve a major pain point. I will start by reviewing #754.