Mark sizeAnalysis APIs as experimental

Add @ApiStatus.Experimental annotations to:
- SizeAnalysisExtension class
- sizeAnalysis configuration function

This marks the new size analysis APIs as experimental and subject
to change, providing appropriate warnings to users.

Closes EME-280

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: runningcode

plugin-build/src/main/kotlin/io/sentry/android/gradle/extensions/SentryPluginExtension.kt

@@ -107,6 +107,7 @@ abstract class SentryPluginExtension @Inject constructor(project: Project) {
 
   val sizeAnalysis: SizeAnalysisExtension = objects.newInstance(SizeAnalysisExtension::class.java)
 
+  @org.jetbrains.annotations.ApiStatus.Experimental
   fun sizeAnalysis(sizeAnalysisAction: Action<SizeAnalysisExtension>) {
     sizeAnalysisAction.execute(sizeAnalysis)
   }

plugin-build/src/main/kotlin/io/sentry/android/gradle/extensions/SizeAnalysisExtension.kt

@@ -5,7 +5,9 @@ import javax.inject.Inject
 import org.gradle.api.model.ObjectFactory
 import org.gradle.api.provider.Property
 import org.gradle.api.provider.ProviderFactory
+import org.jetbrains.annotations.ApiStatus
 
+@ApiStatus.Experimental
 open class SizeAnalysisExtension
 @Inject
 constructor(objects: ObjectFactory, providerFactory: ProviderFactory) {