Fix Groovy compatibility in OpenTelemetrySdkBuilder

[ADITYA-CODE-SOURCE]

Summary

• remove hard incubator-related linkage from OpenTelemetrySdkBuilder so Groovy callers can build the SDK without incubator classes on the classpath
• keep the incubator extension path working through guarded reflective lookup and align OpenTelemetrySdkBuilderUtil with the internal signature change
• add a Groovy regression test and wire Groovy in as a test-only dependency through dependency management

Testing

• ./gradlew --no-daemon --no-parallel -Dorg.gradle.workers.max=1 -Dorg.gradle.jvmargs=\"-Xmx768m -XX:MaxMetaspaceSize=256m\" :sdk:all:spotlessCheck :sdk:all:checkstyleMain :sdk:all:checkstyleTest :sdk:all:test --tests io.opentelemetry.sdk.OpenTelemetrySdkTest

[psx95]

What's the motivation behind this change? Is this related to #8198 ?

[ADITYA-CODE-SOURCE]

What's the motivation behind this change? Is this related to #8198 ?

this is related to #8198.
The motivation for this change is to avoid hard linkage from OpenTelemetrySdkBuilder to incubator-related types, which can cause Groovy callers to fail when those classes are not on the classpath. This PR keeps the existing incubator path intact when available, while allowing OpenTelemetrySdk.builder().build() to work in the non-incubator Groovy case covered by the new regression test.