Remove singleton pattern from ethereum smart contracts setup

[vtleonardo]

Scope

Implementing the singleton pattern for the setup of the Ethereum smart contracts was not a good call since it makes the unit tests way harder to setup. This PR is replacing the singleton pattern with a handlers pattern. This new pattern should make the implementation of multiple layer1 blockchains a little bit easier in the future.

TODO:
Once we start adding new layer1 patterns, we probably will need a handler for layer1 clients and move the events and tasks to their own layer sub-packages.

[ghost]

Some various questions/concerns before sign-off.

[codecov-commenter]

Codecov Report

Merging #72 (67efd9f) into main (fee293c) will decrease coverage by 0.01%.
The diff coverage is 44.44%.

@@            Coverage Diff             @@
##             main      #72      +/-   ##
==========================================
- Coverage   45.62%   45.61%   -0.02%     
==========================================
  Files         214      214              
  Lines       38503    38504       +1     
==========================================
- Hits        17568    17562       -6     
- Misses      19005    19008       +3     
- Partials     1930     1934       +4     

Impacted Files	Coverage Δ
layer1/executor/task_scheduler.go	1.15% <0.00%> (-0.01%)	⬇️
layer1/executor/tasks/dkg/utils/utils.go	7.69% <0.00%> (ø)
layer1/monitor/objects/event_map.go	0.00% <ø> (ø)
layer1/executor/task_manager.go	65.96% <100.00%> (ø)
badgerTrie/smt_merkle_proof.go	60.15% <0.00%> (-4.69%)	⬇️

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