This will make it easier for calling applications to pass outbound proxy
information to the Snowflake library. Non-tor applications and
applications such as Orbot that run PTs in a separate process can now
configure outbound proxies without setting tor-specific environment
variables.

At the moment snowflake is the only transport that supports it, but
this provides some structure for more transports to fully make use of
the pt.Log call or other logging and UX features.

Snowflake has a different set of requirements than other transports for
which proxies are supported, and the snowflake library handles the proxy
configuration, so we need to use a different method for passing proxy
URL information to the Snowflake library.

This adds only Snowflake client support to lyrebird. All configuration
should be done through SOCKS arguments.

chore(deps): update gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/webtunnel digest to e64b1b3

chore(deps): update module gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/webtunnel to v0.0.0-20240507101150-3b6faa481637

chore(deps): update gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/webtunnel digest to c6e11b4

* Closes: #40013