feat(reliable-integration): implement stream ID

[glevco]

Depends on #763

Motivation

Implement an event stream ID so every time the event database is reset, a new ID is generated. This makes it easy for the client to know if he has to reprocess events from the beginning.

Acceptance Criteria

• Add Stream ID generation on EventManager
• Add save_stream_id() and get_stream_id() methods to EventStorage and its implementations
• Reset stream ID in EventStorage.reset_events()
• Add Stream ID to all event responses

Checklist

• If you are requesting a merge into master, confirm this code is production-ready and can be included in future releases as soon as it gets merged

[codecov]

Codecov Report

Patch coverage: 82.35% and no project coverage change.

Comparison is base (a847f51) 84.74% compared to head (7108be4) 84.74%.
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #766   +/-   ##
=======================================
  Coverage   84.74%   84.74%           
=======================================
  Files         259      259           
  Lines       21912    21940   +28     
  Branches     2963     2964    +1     
=======================================
+ Hits        18570    18594   +24     
- Misses       2696     2701    +5     
+ Partials      646      645    -1     

Files Changed	Coverage Δ
hathor/event/storage/rocksdb_storage.py	91.26% <55.55%> (-3.42%)	⬇️
hathor/event/storage/memory_storage.py	98.36% <83.33%> (-1.64%)	⬇️
hathor/event/event_manager.py	91.60% <87.50%> (-0.40%)	⬇️
hathor/event/storage/event_storage.py	100.00% <100.00%> (ø)
hathor/event/websocket/factory.py	93.10% <100.00%> (+0.24%)	⬆️
hathor/event/websocket/response.py	100.00% <100.00%> (ø)

... and 4 files with indirect coverage changes

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The base branch was changed.