Improve Scala compilation caching and build config

[ribafish]

Changes

• Bump scala-maven-plugin from 4.9.6 to 4.9.10 to fix testCompile cache misses
• Bump semanticdb-scalac from 4.9.6 to 4.15.2
• Enhance build cache configuration for scalaCompile tasks:
  • Track sourceDirectory and testSourceDirectory as explicit file inputs
  • Track pluginArtifacts and dependencies as iterated properties instead of ignoring them
  • Track compilerPlugins with IGNORED_PATH normalization
  • Remove classpath from ignored properties (deprecated, included in classpathElements)
• Add .idea/ to .gitignore to exclude IntelliJ IDEA configuration

Impact

These changes improve Maven build caching accuracy by properly tracking all compilation inputs, reducing unnecessary cache misses during incremental builds.

[chibenwa]

Wonderful contribution 👍

Grateful if you could share build time enhancement metrics!

[chibenwa]

Cc @jeantil not sure you have time for this but it will for sure interest you

[jeantil]

Looks good to me, I had already investigated these changes before after clay pointed out https://github.com/gradle/develocity-build-config-samples/pull/2087/changes to me
however at the time there was a bug in the extension and I reverted the changes

when I upgraded the extension back I forgot to apply the changes again

go

(discussion on the ASF slack https://the-asf.slack.com/archives/CF6PY5M4N/p1758051950501649)

[jeantil]

small nitpick

1. this change is unrelated

2. this local env specific exclusion is more relevant in

• $GIT_DIR/info/exclude.
• or a configured global ignore file for your user (usually achieved by setting core.excludesFile)