Add HATS to Euclid Cloud Access tutorial

[troyraen]

https://caltech-ipac.github.io/irsa-tutorials/euclid-cloud-access/

Add something about catalog to the learning goals.

Replace sections "6. Find the MER catalog for a given tile" and "7. Find the MER Object ID for our target" with a section that gets the needed info from the HATS product.
Basic info that could be used to describe the HATS product:

• Merged Objects catalog is an enhanced data product contributed by IRSA. It's not available from on-premises (except for bulk-download only, but don't need to get into that here).
• It's a single Parquet dataset containing most of the data from the Euclid MER, PHZ, and SPE catalogs. Point to https://caltech-ipac.github.io/irsa-tutorials/euclid-q1-hats-intro/ for details and access examples using PyArrow.
• It's formatted as a HATS Collection. Point to https://caltech-ipac.github.io/irsa-tutorials/irsa-hats-with-lsdb/ for details and access examples using LSDB.

Also add a link to https://irsa.ipac.caltech.edu/cloud_access/#euclid somewhere in section "1. Introduction". It has basic bucket and path info and has a link to browsable directories. (Not HATS specific; I just noticed we're not pointing there yet.)