This makes it so you can check if the initial connection
is established. Before this we used reconnect which would
lazily attempt to connect. So if you were trying to connect
to a non existant Server you wouldn't find out until after
you attempted your first RPC. This simplifies everything
by allowing you connect before creating the RPC client.
BREAKING CHANGE: `Endpoint::channel` was removed in favor of
an async `Endpoint::connect`.
This commit reworks TLS configuration of both servers and endpoints in
order to provide a more flexible API. We now add options to configure
the selected TLS library using the appropriate 'native' configuration
structures, as well as retaining the existing simplier interface which
is compatible with both.
The new API can also be easily extended to support simple interfaces for
configuring mTLS and a range of other options without creating sprawl
in the builders for `Server` and `Endpoint`.
