Simplify ScipBuildTool now that it is a Bazel-only worker

ScipBuildTool is dispatched exclusively from IndexCommand.run() when the
Bazel aspect passes --scip-config, so a lot of its surface area was dead
code. Net: -501 lines.

ScipBuildTool:
- No longer extends BuildTool. It does not participate in detection, so
  the name/isHidden/usedInCurrentDirectory overrides served no purpose.
  generateScip() is renamed to run().
- Drop the Kotlin compilation path (~150 lines, K2JVMCompiler, message
  collector, MPP common-source handling). The Bazel aspect only writes
  *.java files to sourceFiles, so this code was unreachable.
- Drop Coursier-based dependency resolution. The aspect passes the full
  classpath directly, never the 'dependencies' field.
- Drop Coursier-based JVM resolution (JvmIndex/JvmCache/JavaHome). The
  aspect always sets 'javaHome'; the worker now requires it.
- Drop the JDK 'kind' branch and module-info partitioning. Bazel never
  sets 'kind'.
- Drop the strictCompilation gate and the in-class ListBuffer that used
  to combine Java + Kotlin compile attempts.
- Slim Config from 13 to 9 fields (drop dependencies, jvm, kind, plus
  the Dependency case class and custom codec).

IndexCommand:
- Drop --strict-compilation (only consumed by the removed code path).
- Drop --scip-ignored-javac-option-prefixes and
  --scip-ignored-annotation-processors. These were never propagated by
  BazelBuildTool to the per-target invocations, so they were dead.

Dependencies.scala:
- Drop kotlinMPPCommon (sole caller was the removed Kotlin compile
  path).

build.sbt:
- Drop the cli project's runtime dependency on kotlin-compiler-embeddable
  and the four kotlin-scripting-* artifacts; nothing in the cli
  references them anymore.

GradleJavaToolchains.scala:
- Drop the @language("Groovy") IDE hint; its provider class was only
  available transitively via the kotlin-compiler-embeddable artifact we
  just removed.

Author: jupblb

build.sbt

@@ -235,14 +235,7 @@ lazy val cli = project
         "io.get-coursier" %% "coursier-jvm" % V.coursier,
         "org.scala-lang.modules" %% "scala-xml" % V.scalaXml,
         "com.lihaoyi" %% "requests" % V.requests,
-        "org.scalameta" %% "moped" % V.moped,
-        "org.jetbrains.kotlin" % "kotlin-compiler-embeddable" % V.kotlinVersion,
-        "org.jetbrains.kotlin" % "kotlin-scripting-common" % V.kotlinVersion,
-        "org.jetbrains.kotlin" % "kotlin-scripting-jvm" % V.kotlinVersion,
-        "org.jetbrains.kotlin" % "kotlin-scripting-dependencies" %
-          V.kotlinVersion,
-        "org.jetbrains.kotlin" % "kotlin-scripting-dependencies-maven" %
-          V.kotlinVersion
+        "org.scalameta" %% "moped" % V.moped
       ),
     (Compile / resourceGenerators) +=
       Def

scip-java/src/main/scala/com/sourcegraph/scip_java/Dependencies.scala

@@ -4,13 +4,11 @@ import java.io.File
 import java.nio.file.Path
 
 import scala.concurrent.duration.Duration
-import scala.util.Try
 import scala.xml.XML
 
 import coursier.Fetch
 import coursier.Repositories
 import coursier.Resolve
-import coursier.cache.Cache
 import coursier.cache.CachePolicy
 import coursier.cache.FileCache
 import coursier.core._
@@ -43,39 +41,6 @@ object Dependencies {
     Repositories.centralGcs
   )
 
-  /**
-   * Attempts to find the "common definitions" JAR for a potentially
-   * MultiPlatform Project. We only support JVM for now, native and JS are not
-   * supported. If it ends with '-jvm', we search for a JAR with the classifier
-   * truncated. If it does not end with -jvm, we search for a JAR with the
-   * -common classifier. This is non-exhaustive, and the classifiers are
-   * completely arbitrary.
-   */
-  def kotlinMPPCommon(
-      group: String,
-      artifact: String,
-      version: String
-  ): Option[Path] =
-    Try {
-      val task = Fetch[Task](Cache.default)
-        .withClassifiers(Set(Classifier.sources))
-        .addRepositories(defaultExtraRepositories: _*)
-
-      if (artifact.endsWith("-jvm")) {
-        val dependency = Dependencies.parseDependency(
-          s"$group:${artifact.stripSuffix("-jvm")}:$version"
-        )
-        val result = task.addDependencies(dependency).runResult()
-        return Some(result.files.head.toPath)
-      }
-
-      val dependency = Dependencies.parseDependency(
-        s"$group:$artifact-common:$version"
-      )
-      val result = task.addDependencies(dependency).runResult()
-      result.files.head.toPath
-    }.toOption
-
   def resolveDependencies(
       dependencies: List[String],
       transitive: Boolean = true

scip-java/src/main/scala/com/sourcegraph/scip_java/buildtools/GradleJavaToolchains.scala

@@ -9,7 +9,6 @@ import scala.jdk.CollectionConverters._
 
 import com.sourcegraph.scip_java.Embedded
 import com.sourcegraph.scip_java.commands.IndexCommand
-import org.intellij.lang.annotations.Language
 
 case class GradleJavaToolchains(
     toolchains: List[GradleJavaCompiler],
@@ -86,7 +85,6 @@ object GradleJavaToolchains {
     )
     val gradleVersionPath = tmp.resolve("gradle-version.txt")
     val taskName = "scipDetectJavaToolchains"
-    @Language("Groovy")
     val script =
       s"""|
           |try {