Fix remote write merging and duplicate function permissions

[mohamedeltawel]

Summary

• Fix remote partial merge behavior so unchanged existing items without write-check fields are preserved instead of failing the write.
• Prevent remote writes from appending new items that are not allowed through the merge path.
• Merge duplicate local feature function permissions with allowed-wins semantics:
  • a later allowed operation upgrades a previously not-allowed operation
  • a later not-allowed declaration does not downgrade an operation already allowed by another use case
• Add regression tests for collection merge behavior, DeviceConfiguration partial writes, and duplicate function permission merging.

[coveralls]

coverage: 93.728% (+0.04%) from 93.691% — fix/MergingAlgorithm into dev