Scope Accuracy Rework

[TheTechromancer]

This PR makes several important changes to BBOT's event handling logic that fixes numerous small and annoying edge cases (including #757, which prompted this effort) and generally simplifies the code.

Because BBOT does speculative discovery via internal events (events that are distributed only to scan modules, but not to output modules - such as far-out DNS resolutions, speculated open ports, unverified URLs, etc.), and because when outputting to a graph such as Neo4j, these chains of events must be preserved to prevent orphans, there was a lot of ugly logic that accumulated over time where we were making special exceptions for Neo4j. This caused unexpected behaviors, and led to even more exceptions for those exceptions, etc.

Originally, I used BBOT's built-in event deduplication logic to shepherd these chains of events and prevent orphans in the graph. But the implementation was overly complex, difficult to maintain and still had bugs. So it has been completely reworked and these two systems have been decoupled.

The result is two cleaner and simpler systems instead of one overly complex one. Extensive tests have been written to ensure the systems work as intended.

By necessity, a new DNS mock system has been added which enables more elaborate and more effective tests.

This was a challenging rework. If you're interested in the details, please see the thread for this issue where I typed out my thought process.

[codecov]

Codecov Report

Attention: 5 lines in your changes are missing coverage. Please review.

Comparison is base (1224dcf) 92% compared to head (99ae8e9) 92%.
Report is 1 commits behind head on dev.

Files	Patch %	Lines
bbot/core/event/base.py	93%	2 Missing ⚠️
bbot/core/helpers/dns.py	98%	1 Missing ⚠️
bbot/scanner/manager.py	99%	1 Missing ⚠️
...bot/test/test_step_1/test_manager_deduplication.py	100%	1 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff           @@
##             dev    #772    +/-   ##
======================================
+ Coverage     92%     92%    +1%     
======================================
  Files        286     287     +1     
  Lines      17290   17901   +611     
======================================
+ Hits       15831   16459   +628     
+ Misses      1459    1442    -17     

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[liquidsec]

I am approving for dev, but my intention is to test this extensively prior to the dev->stable push. However, I can't fully grok all of it in a reasonable amount of time. I see no issues through my review, and the extensive tests add a lot of reassurance. The potential consequences of scope mishaps warrants an extra bit of caution, though.

[batgoose]

Will test changes when able