Merge branch 'feat/app-start-extension-core' into feat/app-start-extension-android

Author: buenaflor

sentry/src/main/java/io/sentry/IAppStartExtender.java

@@ -12,8 +12,17 @@
 @ApiStatus.Internal
 public interface IAppStartExtender {
 
+  /**
+   * Begins extending the app start. Intended to be called from {@code Application.onCreate} right
+   * after SDK init. No-ops if the app start already finished, none is in progress, or it was
+   * already extended (first call wins).
+   */
   void extendAppStart();
 
+  /**
+   * Finishes the extended app start, allowing the app start transaction to complete. No-ops if the
+   * app start was not extended or this was already called.
+   */
   void finishAppStart();
 
   /**