Add Eclipse JDT embedded lockfiles, upgrade formatter version to 4.40

[scordio]

• Closes Embed p2 lockfiles for Eclipse JDT #1996

This PR introduces lockfiles for the Eclipse JDT formatter, falling back to today's behavior via P2 resolution if an embedded lockfile for the selected version doesn't exist.

In addition, the default JDT version is now upgraded to the latest available (4.40), and embedded lockfiles have been added for versions 4.40, 4.39, 4.11, and 4.9. The rationale for covering the last two is only because those versions appeared in test code, but please let me know what the proper version range should be, and I'll happily adjust this PR and/or introduce missing lockfiles.

To support maintenance and future lockfile generation, I added a new EclipseJdtLockfileMetadataTool among the test classes. This class has two main entry points that can be manually invoked to either verify or update the existing lockfiles by resolving org.eclipse.jdt.core versions directly from the metadata available at https://download.eclipse.org/eclipse/updates/. If you think there is a better approach to achieve the same, please let me know, and I'd be happy to update my changes.

Disclaimer: this is my first Spotless contribution and I wasn't familiar with its codebase and internal architecture. For this reason, I used GitHub Copilot to navigate through it, brainstorm on a possible solution, and implement the self-contained EclipseJdtLockfileMetadataTool class to make lockfile maintenance easier. Nevertheless, I went through and updated pretty much everything that Copilot generated.

---

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• a summary of the change
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This makes it easier for the maintainers to quickly release your changes :)

[scordio]

Before creating a pull request, you might want to format (yes, spotless is formatted by spotless) the code and check for possible bugs

./gradlew spotlessApply
./gradlew spotbugsMain

I tried that locally, but it seems I have some cache configuration errors.

Logs

% ./gradlew spotlessApply
Parallel Configuration Cache is an incubating feature.
Calculating task graph as configuration cache cannot be reused because file 'gradle/spotless.gradle' has changed.
Type-safe project accessors is an incubating feature.

6 problems were found storing the configuration cache.
- Task `:lib-extra:spotlessGroovyGradle` of type `com.diffplug.gradle.spotless.SpotlessTaskImpl`: error writing value of type 'com.diffplug.spotless.ConfigurationCacheHackList'
- Task `:lib:spotlessGroovyGradle` of type `com.diffplug.gradle.spotless.SpotlessTaskImpl`: error writing value of type 'com.diffplug.spotless.ConfigurationCacheHackList'
- Task `:plugin-gradle:spotlessGroovyGradle` of type `com.diffplug.gradle.spotless.SpotlessTaskImpl`: error writing value of type 'com.diffplug.spotless.ConfigurationCacheHackList'
- Task `:plugin-maven:spotlessGroovyGradle` of type `com.diffplug.gradle.spotless.SpotlessTaskImpl`: error writing value of type 'com.diffplug.spotless.ConfigurationCacheHackList'
- Task `:spotlessGroovyGradle` of type `com.diffplug.gradle.spotless.SpotlessTaskImpl`: error writing value of type 'com.diffplug.spotless.ConfigurationCacheHackList'
- Task `:testlib:spotlessGroovyGradle` of type `com.diffplug.gradle.spotless.SpotlessTaskImpl`: error writing value of type 'com.diffplug.spotless.ConfigurationCacheHackList'

See the complete report at file:///Users/stefano/Projects/spotless/build/reports/configuration-cache/exlmz05ylu0bpkxw5gri9wjbi/dpcxsijaza6v5jbddk4m3qm4l/configuration-cache-report.html

[Incubating] Problems report is available at: file:///Users/stefano/Projects/spotless/build/reports/problems/problems-report.html

FAILURE: Build failed with an exception.

* What went wrong:
Error while saving task graph
> Configuration cache state could not be cached: field `stepsInternalEquality` of task `:testlib:spotlessGroovyGradle` of type `com.diffplug.gradle.spotless.SpotlessTaskImpl`: error writing value of type 'com.diffplug.spotless.ConfigurationCacheHackList'
   > java.io.IOException: Failed to provision P2 dependencies
> Configuration cache state could not be cached: field `stepsInternalEquality` of task `:lib-extra:spotlessGroovyGradle` of type `com.diffplug.gradle.spotless.SpotlessTaskImpl`: error writing value of type 'com.diffplug.spotless.ConfigurationCacheHackList'
   > java.io.IOException: Failed to provision P2 dependencies
> Configuration cache state could not be cached: field `stepsInternalEquality` of task `:lib:spotlessGroovyGradle` of type `com.diffplug.gradle.spotless.SpotlessTaskImpl`: error writing value of type 'com.diffplug.spotless.ConfigurationCacheHackList'
   > java.io.IOException: Failed to provision P2 dependencies
> Configuration cache state could not be cached: field `stepsInternalEquality` of task `:plugin-maven:spotlessGroovyGradle` of type `com.diffplug.gradle.spotless.SpotlessTaskImpl`: error writing value of type 'com.diffplug.spotless.ConfigurationCacheHackList'
   > java.io.IOException: Failed to provision P2 dependencies
> Configuration cache state could not be cached: field `stepsInternalEquality` of task `:plugin-gradle:spotlessGroovyGradle` of type `com.diffplug.gradle.spotless.SpotlessTaskImpl`: error writing value of type 'com.diffplug.spotless.ConfigurationCacheHackList'
   > java.io.IOException: Failed to provision P2 dependencies
> Configuration cache state could not be cached: field `stepsInternalEquality` of task `:spotlessGroovyGradle` of type `com.diffplug.gradle.spotless.SpotlessTaskImpl`: error writing value of type 'com.diffplug.spotless.ConfigurationCacheHackList'
   > java.io.IOException: Failed to provision P2 dependencies

* Try:
> Run with --stacktrace option to get the stack trace.
> Run with --info or --debug option to get more log output.
> Get more help at https://help.gradle.org.

BUILD FAILED in 542ms
Configuration cache entry discarded due to serialization error.