feat: implementation of IfThenElseCondition

[derekpierre]

Type of PR:

• Bugfix
• Feature
• Documentation
• Other

Required reviews:

• 1
• 2
• 3

What this does:
Based over #591 .

Initial implementation of IfThenElseCondition.

Issues fixed/closed:
Related to nucypher/nucypher#3558.

• Fixes #...

Why it's needed:

Explain how this PR fits in the greater context of the NuCypher Network. E.g.,
if this PR address a nucypher/productdev issue, let reviewers know!

Notes for reviewers:

What should reviewers focus on? Is there a particular commit/function/section
of your PR that requires more attention from reviewers?

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Please upload report for BASE (epic-v0.6.x@7f30464). Learn more about missing BASE report.

Additional details and impacted files

@@              Coverage Diff               @@
##             epic-v0.6.x     #593   +/-   ##
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  Coverage               ?   89.18%           
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  Files                  ?       73           
  Lines                  ?     6490           
  Branches               ?      170           
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  Hits                   ?     5788           
  Misses                 ?      702           
  Partials               ?        0           

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[manumonti]

const lgtm = True
const approved = True
const elseCondition = False

const condition = new IfThenElseCondition({
      ifCondition: lgtm,
      thenCondition: approved,
      elseCondition: elseCondition,
});