refactor: simply the IsSendOutTxProcessed func

[ws4charlie]

Description

1. Reorganize and simplified the EVM IsSendOutTxProcessed method by splitting into smaller/meaningful sub functions, removing duplicate logics.
2. Added unit tests against each split sub function.

Closes: 1534

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 84.27673% with 25 lines in your changes are missing coverage. Please review.

Project coverage is 70.00%. Comparing base (58a1b23) to head (f9cb534).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1989      +/-   ##
===========================================
+ Coverage    68.54%   70.00%   +1.45%     
===========================================
  Files          236      237       +1     
  Lines        13620    13502     -118     
===========================================
+ Hits          9336     9452     +116     
+ Misses        3834     3598     -236     
- Partials       450      452       +2     

Files	Coverage Δ
zetaclient/zetabridge/zetacore_bridge.go	38.66% <100.00%> (-0.41%)	⬇️
zetaclient/evm/inbounds.go	69.32% <85.71%> (ø)
zetaclient/evm/outbound_transaction_data.go	69.33% <50.00%> (ø)
zetaclient/zetabridge/tx.go	52.42% <33.33%> (-0.24%)	⬇️
zetaclient/evm/outbounds.go	96.85% <96.85%> (ø)
zetaclient/zetacore_observer.go	17.91% <0.00%> (ø)
zetaclient/bitcoin/bitcoin_client.go	23.07% <0.00%> (ø)
zetaclient/evm/evm_client.go	20.09% <22.22%> (+5.01%)	⬆️

[github-actions]

!!!WARNING!!!
nosec detected in the following files: zetaclient/evm/evm_client.go

Be very careful about using #nosec in code. It can be a quick way to suppress security warnings and move forward with development, it should be employed with caution. Suppressing warnings with #nosec can hide potentially serious vulnerabilities. Only use #nosec when you're absolutely certain that the security issue is either a false positive or has been mitigated in another way.

Only suppress a single rule (or a specific set of rules) within a section of code, while continuing to scan for other problems. To do this, you can list the rule(s) to be suppressed within the #nosec annotation, e.g: /* #nosec G401 */ or //#nosec G201 G202 G203
Broad #nosec annotations should be avoided, as they can hide other vulnerabilities. The CI will block you from merging this PR until you remove #nosec annotations that do not target specific rules.

Pay extra attention to the way #nosec is being used in the files listed above.

[lumtis]

Looks good to me @kevinssgh can you check sometimes?

[kevinssgh]

Looks pretty good, left some comments.