Use ContextCompat.getMainExecutor when calling MediaBrowser methods

This allows the service to be switched to run in another process and the app still works the same as if it is running in the same process.

Issue: #100
PiperOrigin-RevId: 458460005
(cherry picked from commit c9abe70)

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

@@ -27,6 +27,7 @@ import android.widget.ArrayAdapter
 import android.widget.ListView
 import android.widget.TextView
 import androidx.appcompat.app.AppCompatActivity
+import androidx.core.content.ContextCompat
 import androidx.media3.common.MediaItem
 import androidx.media3.session.LibraryResult
 import androidx.media3.session.MediaBrowser
@@ -164,7 +165,7 @@ class MainActivity : AppCompatActivity() {
         val root: MediaItem = result.value!!
         pushPathStack(root)
       },
-      MoreExecutors.directExecutor()
+      ContextCompat.getMainExecutor(this)
     )
   }
 

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

@@ -29,6 +29,7 @@ import android.widget.LinearLayout
 import android.widget.ListView
 import android.widget.TextView
 import androidx.appcompat.app.AppCompatActivity
+import androidx.core.content.ContextCompat
 import androidx.media3.common.MediaItem
 import androidx.media3.common.Player
 import androidx.media3.session.MediaBrowser
@@ -150,7 +151,7 @@ class PlayableFolderActivity : AppCompatActivity() {
         val result = mediaItemFuture.get()!!
         title.text = result.value!!.mediaMetadata.title
       },
-      MoreExecutors.directExecutor()
+      ContextCompat.getMainExecutor(this)
     )
     childrenFuture.addListener(
       {
@@ -161,7 +162,7 @@ class PlayableFolderActivity : AppCompatActivity() {
         subItemMediaList.addAll(children)
         mediaListAdapter.notifyDataSetChanged()
       },
-      MoreExecutors.directExecutor()
+      ContextCompat.getMainExecutor(this)
     )
   }