NSFS | MPU | Support of part-number parameter for get/head object

[nadavMiz]

Explain the changes

1. add object xattr for parts size and offsets
2. add get and head object for specific part using the parts info attribute list
3. add exception if both part_number and range is defined for get-object like in AWS

Issues: Fixed #xxx / Gap #xxx

1. https://github.com/noobaa/noobaa-core/issues/7226

Testing Instructions:

1. run sudo node ./node_modules/mocha/bin/mocha src/test/unit_tests/test_namespace_fs.js

• [ ] Doc added/updated
• [x] Tests added