Migrate to Sonatype Central Portal

[gpunto]

🎯 Goal

AND-886

OSSRH has been sunset. We should migrate all SDKs away.

🛠 Implementation details

• Use https://github.com/vanniktech/gradle-maven-publish-plugin (already supported by our current CI release actions)
• Remove old publishing-related Gradle files
• Move publishing configuration to the root gradle block

Note: the configuration will be largely migrated to the convention plugins. I'm doing it in two separate steps so first we can do the migration to Central Portal in isolation and verify it works as expected.

Also, requires this to be merged before releasing: GetStream/android-ci-actions#5

🎨 UI Changes

None

🧪 Testing

Locally, you can test doing ./gradlew publishToMavenLocal and verify that the ~/.m2/repository contains what you expect.

☑️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 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
• Check the SDK Size Comparison table in the CI logs

🎉 GIF

Please provide a suitable gif that describes your work on this pull request

[github-actions]

SDK Size Comparison 📏

SDK	Before	After	Difference	Status
stream-chat-android-client	3.23 MB	3.23 MB	0.00 MB	🟢
stream-chat-android-offline	3.45 MB	3.45 MB	0.00 MB	🟢
stream-chat-android-ui-components	10.54 MB	10.54 MB	0.00 MB	🟢
stream-chat-android-compose	12.76 MB	12.76 MB	0.00 MB	🟢

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud