feat(tests/e2e): Multichain e2e test transfer back

[mconcat]

Description

ref: #313

implements:

• Send back from Cosmos chain B -> ETH -> Cosmos chain A
• Send back from Cosmos chain B -> Cosmos chain A -> ETH

---

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• Wrote unit and integration tests.
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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.86%. Comparing base (99575b3) to head (9468c14).
Report is 6 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #381   +/-   ##
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  Coverage   99.86%   99.86%           
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  Files          14       14           
  Lines         731      731           
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  Hits          730      730           
  Misses          1        1           

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[gjermundgaraba]

I think this looks good! 🚀 Great to have a proper test for this!

Plus the nits I added, the name of the tests should also be rename to include the return part. e.g. TestTransferCosmosToEthToCosmosAndBack_Groth16.
Remember to also search for the name and replace in github workflows and any other places it is used.