Add staticcheck CI with refactor

[julian-bcw]

Detailed description:
This PR does two things:

1. Introduces a static analysis pipeline to help prevent potential bugs and security vulnerabilities in the future.
   Specifically, this will check for things like deprecated packages, dead code, and inefficient/redundant function calls and expressions.
2. Refactors the existing code to resolve any alarms.
   • Most of these changes are simplifications and dead code elimination, though there was also a deprecated package in the test cases, as well as an inefficient string comparison. Overall, low priority fixes.

A complete list of the checks in this pipeline can be found here, though I have removed the style checks (ST*) as well as a few “code simplifications” (S1002, S1005, S1008, S1023, S1039) that are more like style preferences.

EDIT: I've also removed check U1000 (no unused variables), because it was causing the E2E tests to fail. I suspect that there was a false alarm. Perhaps a struct needs to be in a certain format to be converted to a JSON or something.

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

Checklist

• Documentation added
• Tests updated

[codecov]

Codecov Report

Merging #722 (7c3c4f8) into main (63a277b) will not change coverage.
The diff coverage is 37.20%.

@@           Coverage Diff           @@
##             main     #722   +/-   ##
=======================================
  Coverage   63.56%   63.56%           
=======================================
  Files          78       78           
  Lines        5676     5676           
=======================================
  Hits         3608     3608           
  Misses       1896     1896           
  Partials      172      172           

Flag	Coverage Δ
unittests	63.56% <37.20%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
.../process/handler/read-only/fee-transfer/handler.go	17.10% <0.00%> (ø)
app/process/watcher/transfer/watcher.go	45.78% <0.00%> (ø)
app/services/contracts/service.go	0.00% <0.00%> (ø)
app/services/pricing/service.go	65.03% <12.50%> (ø)
app/services/assets/assets.go	70.43% <28.57%> (ø)
app/process/watcher/evm/watcher.go	35.24% <33.33%> (ø)
app/clients/evm/client.go	47.97% <50.00%> (ø)
app/clients/hedera/mirror-node/client.go	49.36% <50.00%> (ø)
app/helper/big-numbers/helper.go	58.33% <100.00%> (ø)
app/helper/memo/helper.go	100.00% <100.00%> (ø)
... and 3 more

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[svetlio8]

Could you please sign your commits? It is part of the checks.

[julian-bcw]

@svetlio8 This is strange. All of the commits are signed already. Should I just close this PR and reopen?

[failfmi]

@svetlio8 This is strange. All of the commits are signed already. Should I just close this PR and reopen?

@julian-bcw
Sign-offs and signed commits are two different things:
https://docs.github.com/en/authentication/managing-commit-signature-verification/about-commit-signature-verification

[julian-bcw]

@failfmi Ah, thanks for the explanation! I've signed the commits, and force-pushed.