Optimizing the query_relations long query

[aatanasov-cloudinary]

Hosting platforms like WP Engine have the following SELECT query checks:

• Killed Query: Query terminated because it is over 16,000 characters.
• Long Query: Query noted because it is over 1,024 characters.

With this PR, we ensure the query_relations SELECT queries are lower than 1024 characters.

Approach

• Splitting the query_relations query into chunks.
• Setting a chunk size of 25 relation hashes to ensure the length of each chunk SELECT query is lower than 1024 characters.

QA notes

Before checking out this branch:

• Install Query Monitor.
• Go to some pages with different content (including images and videos) and check the returned rows of this query in Query Monitor.

After checking out this branch:

• Go to the same pages and sum the returned rows of all chunks. The number should match the previous number.
• Grab a few chunks and check if the characters' length exceeds 1024 characters.
• Ensure all Cloudinary delivered images on the front-end are delivered as it was before checking out this branch.

Note: It is expected that the number of hashes be more than the actual images because we also check for sized URLs.

[gabrielcld2]

Tested locally and everything works as expected 👍