sequencer acceptance tests migration to Kotlin

[fluentcrafter]

This PR migrates the acceptance test to Kotlin, mostly using AI.

Further simplification and improvements of the tests will be done in follow-up PRs.

---

Note

Migrates the acceptance test suite to Kotlin, updates Gradle/test tooling and dependencies, and improves plugin error logging.

• Acceptance Tests (Kotlin migration):
  • Rewrite all acceptance tests and shared DSL helpers from Java to Kotlin under src/test/kotlin and src/main/kotlin (e.g., LineaPlugin*TestBase, EngineAPIService, test classes like *Test.kt).
  • Replace Java utility MemoryAppender.java with Kotlin MemoryAppender.kt.
• Build/Gradle:
  • Apply Kotlin minimal conventions in acceptance-tests/build.gradle; wire Kotlin/solidity/web3j generation into compileKotlin/compileTestKotlin.
  • Add dependencies (e.g., :jvm-libs:...:jackson, WireMock) and dedicated acceptanceTests task; disable default test task.
  • Minor cleanup in sequencer/build.gradle (remove global spotless chaining) and root spotless comment tweak.
• Runtime/Logging:
  • Improve fatal error logging in AbstractLineaRequiredPlugin (structured logging; remove printStackTrace).

^{Written by Cursor Bugbot for commit 1b5e00b. This will update automatically on new commits. Configure here.}

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 62.78%. Comparing base (65d4393) to head (3654832).
⚠️ Report is 7 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #1949   +/-   ##
=========================================
  Coverage     62.78%   62.78%           
  Complexity     1536     1536           
=========================================
  Files           411      411           
  Lines         14958    14958           
  Branches       1580     1580           
=========================================
  Hits           9391     9391           
  Misses         4948     4948           
  Partials        619      619           

Flag	Coverage Δ		*Carryforward flag
hardhat	95.93% <ø> (ø)		Carriedforward from 0f14972
kotlin	60.25% <ø> (ø)

*This pull request uses carry forward flags. Click here to find out more.

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[cursor]

Bug: Log4j2 plugin may not be discovered after Kotlin migration

The MemoryAppender class migrated from Java to Kotlin, but the build only configures Java annotation processing for Log4j2 (annotationProcessor 'org.apache.logging.log4j:log4j-core'). The Java annotation processor won't process Kotlin files, so it won't generate the Log4j2Plugins.dat cache file needed for plugin discovery. The log4j2-test.xml configuration references <Memory> appenders without a packages attribute for runtime scanning. Without either kapt for Kotlin annotation processing or a packages attribute in the configuration, the custom Memory appender plugin may not be discovered at runtime.

Additional Locations (1)

• besu-plugins/linea-sequencer/acceptance-tests/src/main/kotlin/linea/plugin/acc/test/utils/MemoryAppender.kt#L24-L27