Implement Support for Protocol::AuthSwitchRequest

[dickson-michael]

Request: Implement support for Protocol::AuthSwitchRequest

Testing: Set up a MySQL 8.0 server with caching_sha2_password as the default. Set up a user with mysql_native_password authentication. Attempt to log in to that user.

Expectation: Login is attempted using mysql_native_password.

Result: Connection closed unexpectedly.

Trace:

1. Client enters Processor::handleHandshake() and sends a response package noting capabilities include CLIENT_PLUGIN_AUTH and requesting authentication using caching_sha2_password.
2. The server replies back with a Protocol::AuthSwitchRequest packet (2c 00 00 02 fe).
3. Client is in Processor::parsePayload() with connectionState === self::ESTABLISHED, and expects the packet to be either 0x00, 0xff, or 0x01.
4. Packet 0xfe is ignored.
5. Connection times out and is closed.