[UpstreamMergeAutomation] Added details to PR description + clean up

[Shreejit-03]

Implementation

• Switched from rt_target_IP to ssh_connection for direct RT target access.
• Updated automation_conf.json and JsonConfig to use ssh_connection.
• Refactored build_and_test to pass ssh_connection into install_and_test_image.
• Normalized merge report key to "Push and PR".
• Added ni/rtos team tag in PR descriptions for quicker reviewer visibility.
• Adjusted clean script path to clean.core-feeds_and_core-images.sh (skip_merge scenario compatible).
• Updated README to reflect SSH changes.

Justification

AB#3174387

Testing

Azure DevOps pipeline run completed successfully.

PRs were auto-created:

• https://github.com/ni/meta-selinux/pull/17
• https://github.com/ni/meta-openembedded/pull/100
• https://github.com/ni/pyrex/pull/19
• https://github.com/ni/openembedded-core/pull/172

Mail report was generated and sent successfully.

@pratheekshasn @rajendra-desai-ni

[pratheekshasn]

You might want to change the PR title and the commit message. Do add some more detail in the commit message after the title.