tests(events): migrate flaky event simulation tests to new format

[glevco]

Some event tests were skipped in #646 for not working correctly. This PR reimplements those tests using the new format introduced by #647.

Acceptance Criteria

• Remove previous event scenarios simulation tests and create new ones
• Remove DummyMiner, as it was probably the cause for the faulty tests, and using simulator triggers is a much better approach

[codecov]

Codecov Report

Merging #649 (4605d97) into master (dd56e0a) will decrease coverage by 0.17%.
The diff coverage is 88.23%.

❗ Current head 4605d97 differs from pull request most recent head 441c255. Consider uploading reports for the commit 441c255 to get more accurate results

@@            Coverage Diff             @@
##           master     #649      +/-   ##
==========================================
- Coverage   84.04%   83.87%   -0.17%     
==========================================
  Files         245      246       +1     
  Lines       20279    20340      +61     
  Branches     2757     2746      -11     
==========================================
+ Hits        17043    17061      +18     
- Misses       2639     2708      +69     
+ Partials      597      571      -26     

Impacted Files	Coverage Δ
hathor/conf/settings.py	97.03% <ø> (-0.03%)	⬇️
hathor/event/model/base_event.py	100.00% <ø> (ø)
hathor/event/model/event_type.py	100.00% <ø> (ø)
hathor/event/websocket/factory.py	92.85% <ø> (ø)
hathor/p2p/sync_v1/downloader.py	83.33% <ø> (ø)
hathor/indexes/deps_index.py	90.56% <66.66%> (+0.18%)	⬆️
hathor/builder/cli_builder.py	73.95% <70.88%> (+2.45%)	⬆️
hathor/manager.py	77.21% <74.39%> (+7.43%)	⬆️
hathor/transaction/block.py	91.78% <78.94%> (+0.58%)	⬆️
hathor/builder/resources_builder.py	94.39% <95.00%> (+0.16%)	⬆️
... and 32 more

... and 10 files with indirect coverage changes

The base branch was changed.