[EFM] Added a service event to update EpochExtensionViewCount

[durkmurder]

#5725

Context

This PR is the last one to implement in order to close linked issue. It introduces a new service event which will be used to update the EpochExtensionViewCount in the KV store. Additionally, I have added a dedicated state machine which parses the service event and applies it to the KV store.
After implementing service event handling I suspect that we will get similar state machines for simple "set-value" style events. To avoid boilerplate we might introduce a solution based on generics or maybe consolidate all the logic in single state machine.

Additionally refactored unit tests using generics to make future extensions to the list of the service events easier.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 63.29114% with 29 lines in your changes missing coverage. Please review.

Project coverage is 41.49%. Comparing base (23159e4) to head (8ff34d9).

Files	Patch %	Lines
model/flow/service_event.go	10.52%	17 Missing ⚠️
state/protocol/protocol_state/kvstore/factory.go	0.00%	5 Missing ⚠️
...l/protocol_state/kvstore/set_value_statemachine.go	83.33%	3 Missing and 1 partial ⚠️
model/flow/kvstore.go	66.66%	2 Missing ⚠️
...col/protocol_state/kvstore/upgrade_statemachine.go	87.50%	1 Missing ⚠️

Additional details and impacted files

@@                   Coverage Diff                    @@
##           feature/efm-recovery    #6272      +/-   ##
========================================================
+ Coverage                 41.48%   41.49%   +0.01%     
========================================================
  Files                      2000     2003       +3     
  Lines                    142559   142613      +54     
========================================================
+ Hits                      59136    59173      +37     
- Misses                    77249    77263      +14     
- Partials                   6174     6177       +3     

Flag	Coverage Δ
unittests	41.49% <63.29%> (+0.01%)	⬆️

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[jordanschalm]

Looks good. Most comments are just fixing some copy-paste errors.

After implementing service event handling I suspect that we will get similar state machines for simple "set-value" style events. To avoid boilerplate we might introduce a solution based on generics or maybe consolidate all the logic in single state machine.

I agree, I think handling all these simple "set a single primitive parameter" cases in the SetValue state machine is a good start.

[AlexHentschel]

solid and very clean code 🎸 with great test coverage 🎶

[AlexHentschel]

random side comment:

• wondering if we should change the type of evolvingState in line 312 to protocol.KVStoreReader

  flow-go/state/protocol/protocol_state/state/protocol_state.go

  Lines 308 to 312 in 91554ed

  	func (s *MutableProtocolState) build(
  	parentStateID flow.Identifier,
  	stateMachines []protocol_state.KeyValueStoreStateMachine,
  	serviceEvents []flow.ServiceEvent,
  	evolvingState protocol_state.KVStoreMutator,

  
  this would reflect that the build method does not change the evolvingState anymore

[durkmurder]

Makes sense, updated.

[AlexHentschel]

thanks for the consolidation. very nice and concise tests now. 👏