Set new playlist and start index with one command

PlayableFolderActivity currently uses two seperate commands
to set the playlist and then seek to the requested item.

This is slightly inefficient and also causes analytics
listeners to believe the first item in the playlist was
briefly active.

#minor-release

Issue: #180
PiperOrigin-RevId: 480031682
(cherry picked from commit 5d6d069)

demos/session/src/main/java/androidx/media3/demo/session/PlayableFolderActivity.kt

@@ -30,6 +30,7 @@ import android.widget.ListView
 import android.widget.TextView
 import androidx.appcompat.app.AppCompatActivity
 import androidx.core.content.ContextCompat
+import androidx.media3.common.C
 import androidx.media3.common.MediaItem
 import androidx.media3.common.Player
 import androidx.media3.session.MediaBrowser
@@ -68,10 +69,13 @@ class PlayableFolderActivity : AppCompatActivity() {
     mediaList.setOnItemClickListener { _, _, position, _ ->
       run {
         val browser = this.browser ?: return@run
-        browser.setMediaItems(subItemMediaList)
+        browser.setMediaItems(
+          subItemMediaList,
+          /* startIndex= */ position,
+          /* startPositionMs= */ C.TIME_UNSET
+        )
         browser.shuffleModeEnabled = false
         browser.prepare()
-        browser.seekToDefaultPosition(/* windowIndex= */ position)
         browser.play()
         val intent = Intent(this, PlayerActivity::class.java)
         startActivity(intent)