doc: Improve ZMQ documentation

[mbildwic]

This PR intends to clarify:

. when ZMQ notifications occur
. the message structure of each topic

Closes #23452 (comment)

[shaavan]

Concept ACK

The description looks good and helps the reader understand the topics in better detail. I agree with these changes. However, there is a minor nit that needs to be addressed.

[0xB10C]

Concept ACK on improving the documentation. Thanks for picking this up!

I left a few comments below that I think should be addressed.

[mbildwic]

Thanks for review @0xB10C and @shaavan . I addressed your suggestions.

[promag]

ACK 079576e

[shaavan]

ACK 079576e

Changes since my last review:

• The definitions of topics are expanded upon. They are now much more detailed and help to understand these terms better.
• A note is added explaining the difference in the representation of 32-byte hashes and RPC interface and block explorer.

There are no critical grammatical mistakes in the updated PR, and I find the expanded description to be logically sound and easy to understand. Great Work @mbildwic!

[tylerchambers]

Thanks! This clears things up.

[shaavan]

reACK 8ce9f74

Changes since my last review:

• Text explaining that the topics are ZMQ multipart has been added for all four topics now.
• Proper explanation of the trigger event has been added for hashtx and hashblock topics. This is done to make the description more robust if there is an ordering change of topics in the future.
• String describing the syntax of rawtx and rawblock is added, along with the previously added syntax of hashtx and hashblock.

I agree with the updated changes.

However, I think the description has become too lengthy, with a lot of repeated content in succession. I don’t exactly know how to tackle this. Maybe bolding or italicizing the main difference between topics might help, but I don’t know if that would be the right approach.

[0xB10C]

ACK 8ce9f74.

If more people agree that bold or italic text would help (as mentioned in #23471 (review)), then please add it. I don't mind but don't think it's crucial.

[theStack]

Concept ACK, thanks for working on this!

[theStack]

This PR adds solid clarifications about the ZMQ topics that will be very helpful for all potential users of the ZMQ interface -- this would have also saved me quite some time in the past. Kudos for expicitely mentioning the fact that rawtx/hashtx notifications appear both when added to the mempool or in new blocks. LGTM!

ACK 9544ab6