Add Network layer BatteryPercentage to ApplicationUplink

[halimi]

Summary

References: #7427

The Network Server already receives the battery percentage via the DevStatus MAC command and stores it. We can forward this value to the Application Server in the ApplicationUplink message.

Changes

• Extend the ApplicationUplink message with the LastBatteryPercentage message
• Add the stored values during the uplink match

Testing

Steps

• Use TTS with a real device
• Check the application uplink message, it should contain the Last Battery Percentage in [0, 100] interval

Results

Regressions

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Notes for Reviewers

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Checklist

• Scope: The referenced issue is addressed, there are no unrelated changes.
• Compatibility: The changes are backwards compatible with existing API, storage, configuration and CLI, according to the compatibility commitments in README.md for the chosen target branch.
• Documentation: Relevant documentation is added or updated.
• Testing: The steps/process to test this feature are clearly explained including testing for regressions.
• Infrastructure: If infrastructural changes (e.g., new RPC, configuration) are needed, a separate issue is created in the infrastructural repositories.
• Changelog: Significant features, behavior changes, deprecations and fixes are added to CHANGELOG.md.
• Commits: Commit messages follow guidelines in CONTRIBUTING.md, there are no fixup commits left.