Use a common connection info struct

[afiffon]

Currently, a terrible dereference is being performed when needing to access connection info (such as dialect) -- This should be move to a simple use of a common Arc everywhere.

For example, in file.rs:

let info = self
            .handle
            .handler
            .upstream
            .handler
            .upstream()
            .handler
            .upstream()
            .negotiate_info()
            .unwrap();
        if info.config.compression_enabled && info.dialect.supports_compression() {
            flags.set_read_compressed(true);
        }