Improve documentation on WM data acquisition

[vkuznet]

Impact of the new feature
Improve existing documentation on WM data acquisition

Is your feature request related to a problem? Please describe.
During training session we found few issues with existing documentation.

Describe the solution you'd like
Here are the list of improvements:

• Fix letter M in request state transition diagram to be McM
• Add Close-out sub-section description
• Add full set of requirements for DBS Injection, like 500 files per block, CMSWEB threshold, etc.
• Add link to AgentStatusWatcher
• Add JobCreator before Work acquisition

Describe alternatives you've considered
None

Additional context

[amaltaro]

Valentin, as we briefly discussed over Mattermost, I would rather close this ticket as "Not Planned" and make the relevant updates still as part of the original ticket: #11846

Other than the DBS block closure documentation - which is somehow unrelated to this activity - everything has been covered in this MR https://gitlab.cern.ch/dmwm/wmcore-docs/-/merge_requests/28

I am closing this one, but please let me know if you have different thoughts.