[Access] Add implementation for events data providers

[AndriiDiachuk]

Closes: #6588

In this PR EventsDataProvider was implemented which is responsible for providing events.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 54.36409% with 183 lines in your changes missing coverage. Please review.

Project coverage is 41.23%. Comparing base (8a3055c) to head (dca9a25).

Files with missing lines	Patch %	Lines
.../rest/websockets/data_providers/blocks_provider.go	61.33%	25 Missing and 4 partials ⚠️
...ckets/data_providers/mock/data_provider_factory.go	0.00%	28 Missing ⚠️
...st/websockets/data_providers/mock/data_provider.go	0.00%	24 Missing ⚠️
.../rest/websockets/data_providers/events_provider.go	78.49%	14 Missing and 6 partials ⚠️
...ebsockets/data_providers/block_digests_provider.go	57.89%	14 Missing and 2 partials ⚠️
...ebsockets/data_providers/block_headers_provider.go	57.89%	14 Missing and 2 partials ⚠️
engine/access/rest/websockets/controller.go	0.00%	13 Missing ⚠️
access/handler.go	0.00%	10 Missing ⚠️
engine/access/state_stream/backend/handler.go	18.18%	9 Missing ⚠️
engine/access/subscription/util.go	0.00%	8 Missing ⚠️
... and 7 more

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6766      +/-   ##
==========================================
- Coverage   41.26%   41.23%   -0.03%     
==========================================
  Files        2061     2067       +6     
  Lines      182702   183017     +315     
==========================================
+ Hits        75384    75460      +76     
- Misses     101010   101238     +228     
- Partials     6308     6319      +11     

Flag	Coverage Δ
unittests	41.23% <54.36%> (-0.03%)	⬇️

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