[ISSUE-4262] Stop showing empty state before showing channels

[leandroBorgesFerreira]

🎯 Goal

Stop showing the empty state screen every time the SDK loads channels without database data.

🛠 Implementation details

• Separating setLoadingMore and setLoadingFirstPage and letting the called decide which one is desired.
• Calling setLoading = false after the data is already loaded.

🎨 UI Changes

Before	After

🧪 Testing

Load channels without after cleaning the data of the sample app.

☑️Contributor Checklist

General

• [x] I have signed the Stream CLA (required)
• [x] Assigned a person / code owner group (required)
• [x] Thread with the PR link started in a respective Slack channel (#android-chat-core or #android-chat-ui) (required)
• [x] PR targets the develop branch
• [x] 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~
• [x] Comparison screenshots added for visual changes
• [x] 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

🎉 GIF

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