Load thread data in MessageListController if initially opened for a thread

[VelikovPetar]

🎯 Goal

Proposal:

• Currently when we are instantiating a MessageListController with a parentMessageId (in order to focus a message in a thread, or to open a thread), we are experiencing a small flicker: First the default message list is shown for a brief moment, and then it automatically switches to thread mode. (mostly noticeable on lower end devices (tested on Samsung A05))

The idea of this PR is to remove this flicker, by ensuring that we don't show the default message list, but rather directly enter the thread view.

🛠 Implementation details

1. Change the init block in the MessageListController such that if it is started with a parentMessageId, it enters thread mode immediately. After the operation is complete, ensure the clientState is observed (so that going back from the thread mode properly returns the user to the default message list)
2. Remove the enterThreadSequential invocation from processMessageId -> it will already be invoked in the init block, before calling the processMessageId
3. Rename the processMessageId method to initialFocusMessage - as it only handles the initial focusing of the message.

Important: This change has a side effect, that the user can now start the MessageListController with a parentMessageId but without messageId (previously not possible). The parentMessageId will serve as an indicator that a thread from the parentMessageId should be initially opened, and the messageId will continue to act as the target message to be initially highlighted/focused.

🎨 UI Changes

Before	After
controller-before.mp4	controller-after.mp4

🧪 Testing

Threads case:

1. Open compose sample app
2. Open 'Threads' tab
3. Click on a thread
4. There shouldn't be a flicker when opening the thread

Search case:

1. Open compose sample app
2. Search for a message in a thread
3. Click on the search result
4. There shouldn't be a flicker when opening and highlighting the thread reply