For #17803 - Use the main looper for Handler()s

This was already the one inferred.
Targeting Android 11 means we need to pass it explicitly.

app/src/main/java/org/mozilla/fenix/collections/CollectionCreationView.kt

@@ -5,6 +5,7 @@
 package org.mozilla.fenix.collections
 
 import android.os.Handler
+import android.os.Looper
 import android.text.InputFilter
 import android.view.KeyEvent
 import android.view.LayoutInflater
@@ -168,7 +169,7 @@ class CollectionCreationView(
             text = context.getString(R.string.create_collection_name_collection)
             setOnClickListener {
                 name_collection_edittext.hideKeyboard()
-                val handler = Handler()
+                val handler = Handler(Looper.getMainLooper())
                 handler.postDelayed({
                     interactor.onBackPressed(SaveCollectionStep.NameCollection)
                 }, TRANSITION_DURATION)
@@ -214,7 +215,7 @@ class CollectionCreationView(
             text = context.getString(R.string.collection_rename)
             setOnClickListener {
                 name_collection_edittext.hideKeyboard()
-                val handler = Handler()
+                val handler = Handler(Looper.getMainLooper())
                 handler.postDelayed({
                     interactor.onBackPressed(SaveCollectionStep.RenameCollection)
                 }, TRANSITION_DURATION)

app/src/main/java/org/mozilla/fenix/settings/SettingsFragment.kt

@@ -14,6 +14,7 @@ import android.net.Uri
 import android.os.Build
 import android.os.Bundle
 import android.os.Handler
+import android.os.Looper
 import android.view.LayoutInflater
 import android.widget.Toast
 import androidx.annotation.VisibleForTesting
@@ -335,7 +336,7 @@ class SettingsFragment : PreferenceFragmentCompat() {
                             Toast.LENGTH_LONG
                         ).show()
 
-                        Handler().postDelayed({
+                        Handler(Looper.getMainLooper()).postDelayed({
                             exitProcess(0)
                         }, AMO_COLLECTION_OVERRIDE_EXIT_DELAY)
                     }
@@ -406,7 +407,7 @@ class SettingsFragment : PreferenceFragmentCompat() {
                         getString(R.string.toast_override_fxa_sync_server_done),
                         Toast.LENGTH_LONG
                     ).show()
-                    Handler().postDelayed({
+                    Handler(Looper.getMainLooper()).postDelayed({
                         exitProcess(0)
                     }, FXA_SYNC_OVERRIDE_EXIT_DELAY)
                 }