user tracking – What information about me do stores get through my credit card?

At the very least, they can get the card number. Most receipts will carry even the last digits of the printed card number, but the system will have had the full number at a given time, and may well contain a token version of the PCI-authorized card number (think of it as a value random that can be linked to the card number by the tokenising service). As the same card probably gives the same token each time (technically, it's optional, but as this gives more information than the alternative, it's the most common) they can go "this card also bought X, Y and Z on these Rendezvous".

However, they generally can not reference this data with other stores: the token associated with a given card from store A has no link with the one associated with a particular card from store B, in a system designed in a sensible way. I do not know if a token provider is aggregating data from multiple clients, but this could be a potential nightmare in the GDPR, so I guess that is not the case, at least in Europe.

The issuing bank may also find that purchases are made, of course, but usually by transaction and not by individual item. This does not mean that they can not make informed assumptions about purchases (for example, if you make a payment to a company called "99p Donuts" for 99p, that's a pretty sure assumption that you bought a donut …),