test: synthetic eth txs unit tests

[skosito]

Description

NOTE: don't merge yet, base branch is different PR that should be merged first.

Adds more unit tests to test changes introduced in #2282. A bit tricky to test this with unit tests as it requires a lot of setup and mocking but should be good enough to confirm happy paths are working fine. Ideal testing is with some livenet with explorer, we can discuss in summary doc how to test manually.

Closes: #2301

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Include instructions and any relevant details so others can reproduce.

• Tested CCTX in localnet
• Tested in development environment
• Go unit tests
• Go integration tests
• Tested via GitHub Actions

Checklist:

• I have added unit tests that prove my fix feature works

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Please upload report for BASE (develop@a292450). Learn more about missing BASE report.

Additional details and impacted files

@@            Coverage Diff             @@
##             develop    #2342   +/-   ##
==========================================
  Coverage           ?   68.74%           
==========================================
  Files              ?      302           
  Lines              ?    19180           
  Branches           ?        0           
==========================================
  Hits               ?    13186           
  Misses             ?     5347           
  Partials           ?      647           

Files	Coverage Δ
x/fungible/keeper/evm.go	87.81% <ø> (ø)
rpc/types/events.go	44.49% <0.00%> (ø)

[lumtis]

LGTM, minor comments

Ideal testing is with some livenet with explorer, we can discuss in summary doc how to test manually.

Maybe with a E2E test?

[skosito]

LGTM, minor comments

Ideal testing is with some livenet with explorer, we can discuss in summary doc how to test manually.

Maybe with a E2E test?

yes lets discuss how to add e2e tests maybe