[3786] Show footer before system messages

[bychkovdmitry]

🎯 Goal

Closes #3786

A system message can be the last message in a group if it contains the same user. As a result, the avatar is not displayed for the group.

🎨 UI Changes

Before	After

🧪 Testing

1. User A: Send several messages in a channel and leave the channel
2. User B: Navigate to the channel above
3. Ensure that an avatar is displayed for the last message

☑️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

[filbabic]

☑️Reviewer Checklist

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