add iterator on etcd adapter

[chrisllontop]

Please check if the PR fulfills these requirements

• Followed the Contributing guidelines.
• Tests for the changes have been added (for bug fixes/features) with 100% code coverage.
• Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (294661a) 100.00% compared to head (8bd9192) 100.00%.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #857   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           21        21           
  Lines         2573      2584   +11     
  Branches       335       338    +3     
=========================================
+ Hits          2573      2584   +11     

Impacted Files	Coverage Δ
packages/etcd/src/index.ts	100.00% <100.00%> (ø)

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