Additional logging

[benjben]

Additional DEBUG logs:

• Log the size of the biggest event of a chunk (an event being a collector payload that can contain several actual events)
• Log how many events a collector payload contains

For each event (identified by event_id):

• Log when the contexts are going to be validated
• Log when the contexts have been validated
• Log when the enrichments are going to be executed
• Log when the enrichments have been executed
• Log when the contexts added by the enrichments are going to be validated
• Log when the contexts added by the enrichments have been validated

[benjben]

Yeah way too costly. I removed the lines that are per event to keep only the ones that are by chunk and by collector payload