Add initial nimbus implementation

[stdevMac]

Changes:

• Add a initial nimbus implementation for consensus, validator and import and key exporter.

Types of changes

• New feature (non-breaking change which adds functionality)

Testing

Requires testing

• Yes

In case you checked yes, did you write tests?

• Yes

Should be run also a validator using our stack with nimbus

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 17.12329% with 121 lines in your changes missing coverage. Please review.

Project coverage is 86.26%. Comparing base (000cc79) to head (43de0af).

Files with missing lines	Patch %	Lines
cli/actions/importKeys.go	1.96%	98 Missing and 2 partials ⚠️
cli/actions/slashing.go	40.00%	14 Missing and 1 partial ⚠️
cli/importKeys.go	45.45%	4 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #388      +/-   ##
===========================================
- Coverage    88.06%   86.26%   -1.81%     
===========================================
  Files           99       99              
  Lines         5673     5808     +135     
===========================================
+ Hits          4996     5010      +14     
- Misses         553      669     +116     
- Partials       124      129       +5     

Flag	Coverage Δ
unittests	86.26% <17.12%> (-1.81%)	⬇️

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