[PBE-6017] message list does not scroll on new msg

[kanat]

🎯 Goal

Closes:

• https://stream-io.atlassian.net/browse/PBE-6017

Related PR:

• [PBE-3881] message list scrolls down on reaction #5280

ℹ️ Details

It seems like this is a side effect of the fix for XML (#5280).
NewMessageState changes too fast for Compose to reflect all state changes, that leads to position where Compose thinks that nothing has changed.

I've revisited scrolling logic in both XML and Compose:

1. NewMessageState should always reflect latest new message, we only change it when a new message is being received
2. Re-fixed XML scrolling behaviour in MessageListScrollHelper
3. Added a new test to MessageListControllerTests to make sure we won't break statement from N1

☑️Contributor Checklist

General

• I have signed the Stream CLA (required)
• Assigned a person / code owner group (required)
• Thread with the PR link started in a respective Slack channel (#android-chat-core or #android-chat-ui) (required)
• PR targets the develop branch
• PR is linked to the GitHub issue it resolves

Code & documentation

• Changelog is updated with client-facing changes
• New code is covered by unit tests
• Comparison screenshots added for visual changes
• Affected documentation updated (KDocs, docusaurus, tutorial)

☑️Reviewer Checklist

• UI Components sample runs & works
• Compose sample runs & works
• UI Changes correct (before & after images)
• Bugs validated (bugfixes)
• New feature tested and works
• Release notes and docs clearly describe changes
• All code we touched has new or updated KDocs

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