[REFAC] Fan out processEvent stage to be parallel

[NDStrahilevitz]

Prerequisites

Select one OR another:

• [x] I have discussed the refactoring idea with one (or another) maintainer.
• [x] I'll create a PR to implement this refactoring idea (assign to yourself).
• [ ] Someone else should implement this (describe it well).

Refactoring description

In order to further optimize enrichment logic, me and @rafaeldtinoco discussed splitting the processEvents stage as a parallel pipeline stage. After splitting it, the enrichment stage could be simplified to simply queue until the enrichment info is available from a cgroup_mkdir side effect.