(DOCSP-25168): Add note about MainActor in async/await realm examples (#2165)

* Add note about MainActor in async/await realm examples
* Remove new tip where it's not needed

Author: dacharyc

source/includes/swift-async-await-support.rst

@@ -18,3 +18,6 @@ meet these requirements:
    * - 10.15.0 or 10.16.0
      - Swift 5.5
      - iOS 15.x
+
+If your app accesses Realm in an ``async/await`` context, mark the code 
+with ``@MainActor`` to avoid threading-related crashes.

source/includes/swift-concurrency-mainactor.rst

@@ -0,0 +1,4 @@
+.. tip::
+
+   If your app accesses Realm in an ``async/await`` context, mark the code 
+   with ``@MainActor`` to avoid threading-related crashes.

source/sdk/swift/crud/threading.txt

@@ -283,6 +283,8 @@ and results, on a struct or class property, or on a function parameter.
    parameter. This is useful for functions that may run asynchronously
    or on another thread.
 
+   .. include:: /includes/swift-concurrency-mainactor.rst
+
    .. literalinclude:: /examples/generated/code/start/Threading.snippet.threadsafe-wrapper-function-parameter.swift
       :language: swift
 

source/sdk/swift/quick-start.txt

@@ -159,6 +159,8 @@ what data the realm can read and write.
 Once you have a realm with a subscription, this example passes the realm 
 and the user to another function where you can use the realm.
 
+.. include:: /includes/swift-concurrency-mainactor.rst
+
 .. literalinclude:: /examples/generated/code/start/QuickStartFlexSync.snippet.open-synced-realm.swift
    :language: swift
 

source/sdk/swift/realm-files/bundle-a-realm.txt

@@ -83,6 +83,8 @@ Create a Realm File for Bundling
 #. Use the :swift-sdk:`writeCopy(configuration:) <Structs/Realm.html#/s:10RealmSwift0A0V9writeCopy13configurationyAC13ConfigurationV_tKF>` 
    method to copy the realm to a new file:
 
+.. include:: /includes/swift-concurrency-mainactor.rst
+
 .. literalinclude:: /examples/generated/code/start/BundleRealms.snippet.copy-synced-realm-for-bundling.swift
    :language: swift
 
@@ -139,6 +141,8 @@ application, you need to add code to use it. Use the :swift-sdk:`seedFilePath
 method when configuring your realm to open the realm
 from the bundled file:
 
+.. include:: /includes/swift-concurrency-mainactor.rst
+
 .. literalinclude:: /examples/generated/code/start/BundleRealms.snippet.open-bundled-synced-realm.swift
    :language: swift
 

source/sdk/swift/sync/add-sync-to-app.txt

@@ -71,6 +71,8 @@ Add Device Sync to a Client Application
       types <ios-provide-a-subset-of-classes-to-a-realm>` that we want to 
       include in this realm.
 
+      .. include:: /includes/swift-concurrency-mainactor.rst
+
       .. literalinclude:: /examples/generated/code/start/AddSyncToApp.snippet.open-synced-realm.swift
          :language: swift
 

source/sdk/swift/sync/configure-and-open-a-synced-realm.txt

@@ -167,6 +167,8 @@ Open a Synced Realm for Flexible Sync
 When you use Flexible Sync, use the ``flexibleSyncConfiguration()``
 to open a synced realm. 
 
+.. include:: /includes/swift-concurrency-mainactor.rst
+
 .. literalinclude:: /examples/generated/code/start/FlexibleSync.snippet.flex-sync-open-realm.swift
    :language: swift
 
@@ -195,6 +197,8 @@ open the copy as a synced realm for that user.
 
 .. include:: /includes/note-writecopy-pbs-only.rst
 
+.. include:: /includes/swift-concurrency-mainactor.rst
+
 .. literalinclude:: /examples/generated/code/start/ConvertSyncLocalRealms.snippet.convert-sync-to-sync.swift
    :language: swift
 
@@ -219,6 +223,8 @@ the App Services backend.
 
 .. include:: /includes/note-writecopy-pbs-only.rst
 
+.. include:: /includes/swift-concurrency-mainactor.rst
+
 .. literalinclude:: /examples/generated/code/start/ConvertSyncLocalRealms.snippet.convert-local-to-sync.swift
    :language: swift
 
@@ -250,6 +256,8 @@ non-synced realm. Any changes you make to the non-synced realm reflect
 only in the local realm file. No changes propogate to other devices or
 the App Services backend.
 
+.. include:: /includes/swift-concurrency-mainactor.rst
+
 .. literalinclude:: /examples/generated/code/start/ConvertSyncLocalRealms.snippet.convert-sync-to-local.swift
    :language: swift
 
@@ -275,6 +283,8 @@ This parameter accepts a case from the ``OpenBehavior`` enum:
   populate a realm with initial data, but enables offline-first 
   functionality on subsequent opens.
 
+.. include:: /includes/swift-concurrency-mainactor.rst
+
 .. include:: /examples/generated/code/start/Sync.snippet.specify-download-behavior.swift.rst
 
 .. _ios-open-a-synced-realm-offline:
@@ -288,5 +298,7 @@ You can only open a synced realm offline if you do not require your client
 app to ``always`` :ref:`download changes before opening the realm 
 <ios-specify-download-behavior>`.
 
+.. include:: /includes/swift-concurrency-mainactor.rst
+
 .. literalinclude:: /examples/generated/code/start/Authenticate.snippet.offline-login.swift
    :language: swift

source/sdk/swift/sync/flexible-sync.txt

@@ -138,6 +138,8 @@ Add a Subscription
 Add a subscription in a subscriptions update block. You append each
 new subscription to the client's Realm subscriptions.
 
+.. include:: /includes/swift-concurrency-mainactor.rst
+
 .. literalinclude:: /examples/generated/code/start/FlexibleSync.snippet.add-single-subscription.swift
    :language: swift
 
@@ -252,6 +254,8 @@ error if the update cannot complete successfully.
       }
    }
 
+.. include:: /includes/swift-concurrency-mainactor.rst
+
 SyncSubscriptionState Enum
 ``````````````````````````