Support ipv6 link-local addresses

[socs]

URL parsing fails on ipv6 link-local addresses, eg

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let _ = redis::Client::open("[fe80::1%foo]:6379")?; // -> Error: Redis URL did not parse
    Ok(())
}

This works with redis-cli

# redis-cli -h fe80::1%foo -p 6379
[fe80::1%foo]:6379> ping
PONG

The limitation stems from rust-url library which follows a url spec that omits zone identifier on ipv6 ll addresses.
Perhaps a custom parser could be used by redis-rs, such as the one in redis-cli, so that ipv6 ll addresses is accepted.

[djc]

Should be fixed with #679.