test: add tests for 27-gmp module

[vaporif]

Description

• Add comprehensive unit tests for the GMP module
• Fix nil pointer bug in UnmarshalAcknowledgement for Protobuf encoding (would panic when ack handling is implemented)
• Ignore e2e directory in codecov

---

Before we can merge this PR, please make sure that all the following items have been
checked off. If any of the checklist items are not applicable, please leave them but
write a little note why.

• Linked to GitHub issue with discussion and accepted design, OR link to spec that describes this work.
• Include changelog entry when appropriate (e.g. chores should be omitted from changelog).
• Wrote unit and integration tests if relevant.
• Updated documentation (docs/) if anything is changed.
• Added godoc comments if relevant.
• Self-reviewed Files changed in the GitHub PR explorer.
• Provide a conventional commit message to follow the repository standards.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 64.54%. Comparing base (0c4e6c6) to head (2063590).

Additional details and impacted files

@@                      Coverage Diff                      @@
##           serdar/xxx-contract-calls    #8728      +/-   ##
=============================================================
+ Coverage                      56.68%   64.54%   +7.86%     
=============================================================
  Files                            345      331      -14     
  Lines                          19118    17540    -1578     
=============================================================
+ Hits                           10837    11322     +485     
+ Misses                          7632     5529    -2103     
- Partials                         649      689      +40     

Flag	Coverage Δ
08-wasm	64.81% <ø> (ø)
e2e	?
ibc-go	64.54% <100.00%> (+2.94%)	⬆️

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