CREATE SERVER needs tweaks for compatibility with CONNECT engine

The CREATE SERVER command needs to be tweaked to provide better compatibility with CONNECT engine. It can be accomplished as follows:

#1
Extend the length of the mysql.servers.Host column to 2048 chars (to support CONNECT engine's use of this column for the host connection URL which can easily run to 500 or even 1,000+ chars with certain sets of connection properties)

#2
Extend the length of the mysql.servers.Owner column to 512 chars (to support CONNECT engine's use of this column for storing multiple additional connection options)

#3
Fix the forced lower casing of the host column - right now create server forces the host data to lower case, which is incorrect when storing a host connection URL for connect engine that may contain case sensitive parameters such as passwords and security tokens.

This issue is related to MDEV-13136 which solved part of the problem but requires the above fixes to work properly.