Implement a cache tag minification exactly like purge
This is an implementation of the minification exactly like purge implemented. It is done in a way so that it can be used by both the request finalizer that sets the surrogate keys and the cache tag invalidator that invalidates the keys on the pantheon edge.
The minification uses md5, and expands the entropy with base64 limits to 4 chars
Contains some logging for debugging which I plan on removing before it is complete
Closes #3240286