Clean up trilogy error translation

This commit makes a few changes to our trilogy error translation:

* trilogy-libraries/trilogy#118 introduced
  `Trilogy::EOFError` which we can use instead of matching on
  `TRILOGY_CLOSED_CONNECTION`.
* trilogy-libraries/trilogy#15 introduced
  `Trilogy::ConnectionClosed`, which inherits from `IOError` for
  backwards compatibility. As far as I can tell that's the only
  `IOError` trilogy can raise, so this commit rescues the
  trilogy-specific error instead.
* As far as I can tell Trilogy does not raise `SocketError`, so don't
  bother translating that
* Don't treat TRILOGY_UNEXPECTED_PACKET as a connection error. If we get
  this, it's probably a bug in trilogy that we should fix. I'd like to
  eventually get rid of TRILOGY_INVALID_SEQUENCE_ID too, but we're
  currently relying on it in a few tests (related to trilogy missing
  caching_sha2_password auth support, if I recall correctly)

I'm kinda hoping we'll eventually be able to simplify this to something
like:

```rb
if exception.is_a?(Trilogy::ConnectionError)
  ConnectionFailed.new(message, connection_pool: @pool)
else
  super
end
```

but we'd need more changes to trilogy before that is possible.

activerecord/lib/active_record/connection_adapters/trilogy_adapter.rb

@@ -202,11 +202,10 @@ def translate_exception(exception, message:, sql:, binds:)
           end
 
           case exception
-          when SocketError, IOError
+          when ::Trilogy::ConnectionClosed, ::Trilogy::EOFError
             return ConnectionFailed.new(message, connection_pool: @pool)
           when ::Trilogy::Error
-            if /TRILOGY_CLOSED_CONNECTION|TRILOGY_INVALID_SEQUENCE_ID|TRILOGY_UNEXPECTED_PACKET/.match?(exception.message) ||
-                exception.is_a?(SystemCallError)
+            if exception.is_a?(SystemCallError) || /TRILOGY_INVALID_SEQUENCE_ID/.match?(exception.message)
               return ConnectionFailed.new(message, connection_pool: @pool)
             end
           end