Convert examples/distro build from Groovy to Kotlin DSL

Convert the examples/distro/build.gradle to build.gradle.kts using
Kotlin DSL syntax. This improves type safety and IDE support while
maintaining all existing functionality.

Key changes:
- Rename build.gradle to build.gradle.kts
- Convert Groovy syntax to Kotlin DSL:
  - Use mapOf() instead of Groovy maps
  - Use apply(plugin = "name") instead of apply plugin: "name"
  - Use plugins.withType<JavaPlugin> for deferred configuration
  - Use tasks.named<Type>() for task configuration
- Update .github/scripts/update-sdk-version.sh to match new Kotlin
  DSL syntax ("opentelemetrySdk" to "version" format)
- Preserve extra["versions"] and extra["deps"] for use by Groovy
  subproject build files and applied scripts
- Set Java 8 release only for main source compilation (compileJava),
  allowing tests to use modern Java features

The conversion maintains equivalence to the original Groovy build
while following Gradle Kotlin DSL best practices.

Signed-off-by: Sibasis Padhi <sibasis.padhi@gmail.com>

Author: sibasispadhi

.github/scripts/update-sdk-version.sh

@@ -4,6 +4,6 @@ version=$1
 
 sed -Ei "s/val otelSdkVersion = \"[^\"]*\"/val otelSdkVersion = \"$version\"/" dependencyManagement/build.gradle.kts
 
-sed -Ei "s/(opentelemetrySdk *: )\"[^\"]*\"/\1\"$version\"/" examples/distro/build.gradle
+sed -Ei "s/(\"opentelemetrySdk\" to )\"[^\"]*\"/\1\"$version\"/" examples/distro/build.gradle.kts
 
 sed -Ei "s/(opentelemetrySdk *: )\"[^\"]*\"/\1\"$version\"/" examples/extension/build.gradle

examples/distro/build.gradle

@@ -0,0 +1,88 @@
+group = "io.opentelemetry.example"
+version = "1.0-SNAPSHOT"
+
+buildscript {
+  repositories {
+    maven {
+      url = uri("https://plugins.gradle.org/m2/")
+    }
+    maven {
+      name = "sonatype"
+      url = uri("https://central.sonatype.com/repository/maven-snapshots/")
+    }
+  }
+  dependencies {
+    classpath("com.diffplug.spotless:spotless-plugin-gradle:8.1.0")
+    classpath("com.gradleup.shadow:shadow-gradle-plugin:9.3.1")
+    classpath("io.opentelemetry.instrumentation:gradle-plugins:2.24.0-alpha-SNAPSHOT")
+  }
+}
+
+subprojects {
+  version = rootProject.version
+
+  apply(plugin = "java")
+  apply(plugin = "com.diffplug.spotless")
+
+  val versions = mapOf(
+    // this line is managed by .github/scripts/update-sdk-version.sh
+    "opentelemetrySdk" to "1.57.0",
+
+    // these lines are managed by .github/scripts/update-version.sh
+    "opentelemetryJavaagent" to "2.24.0-SNAPSHOT",
+    "opentelemetryJavaagentAlpha" to "2.24.0-alpha-SNAPSHOT",
+
+    "autoservice" to "1.1.1"
+  )
+
+  val deps = mapOf(
+    "autoservice" to listOf(
+      "com.google.auto.service:auto-service:${versions["autoservice"]}",
+      "com.google.auto.service:auto-service-annotations:${versions["autoservice"]}"
+    )
+  )
+
+  extra["versions"] = versions
+  extra["deps"] = deps
+
+  repositories {
+    mavenCentral()
+    maven {
+      name = "sonatype"
+      url = uri("https://central.sonatype.com/repository/maven-snapshots/")
+    }
+  }
+
+  configure<com.diffplug.gradle.spotless.SpotlessExtension> {
+    java {
+      googleJavaFormat()
+      licenseHeaderFile(rootProject.file("../../buildscripts/spotless.license.java"), "(package|import|public)")
+      target("src/**/*.java")
+    }
+  }
+
+  plugins.withType<JavaPlugin> {
+    dependencies {
+      add("implementation", platform("io.opentelemetry:opentelemetry-bom:${versions["opentelemetrySdk"]}"))
+
+      // these serve as a test of the instrumentation boms
+      add("implementation", platform("io.opentelemetry.instrumentation:opentelemetry-instrumentation-bom:${versions["opentelemetryJavaagent"]}"))
+      add("implementation", platform("io.opentelemetry.instrumentation:opentelemetry-instrumentation-bom-alpha:${versions["opentelemetryJavaagentAlpha"]}"))
+
+      add("testImplementation", "org.mockito:mockito-core:5.21.0")
+
+      add("testImplementation", enforcedPlatform("org.junit:junit-bom:5.14.2"))
+      add("testImplementation", "org.junit.jupiter:junit-jupiter-api")
+      add("testRuntimeOnly", "org.junit.jupiter:junit-jupiter-engine")
+      add("testRuntimeOnly", "org.junit.platform:junit-platform-launcher")
+    }
+  }
+
+  tasks.named<Test>("test") {
+    useJUnitPlatform()
+  }
+
+  tasks.named<JavaCompile>("compileJava") {
+    options.release.set(8)
+  }
+}