Support URLs up to 2048 characters

[Boefjim]

Description

Since some of our redirects contain some large query parameters, we would like the URL field limit to be increased to 2048 characters (this is a generally agreed upon limit, although no exact limit has been defined nor enforced).

Since column indexes only work for columns up to 255 characters, I have added an additional MD5 hashed column.
Since a MD5 hash is always 32 characters long, this can be indexed and should be decently unique.
I have adjusted the queries to use this new indexed column, so the speed of these queries should be similar to how they were.
The queries will still ensure the actual URL matches, since there is still a chance for different URLs to have the same MD5 hash.

I also noticed that when publishing the migrations of the plugin, they are ordered alphabetically, which does not run properly (since adding a description column to the redirects table happens before the redirects table even exists).
So I have also adjusted this so that it adds a single second to the timestamp of the migrations that should be run after the original tables are created (including these new migrations), making it easier to use the plugin.

[riasvdv]

Thank you for this!