replace SyncedFileState.java by Kotlin SyncedFileState.kt

Description

Replace SyncedFileState.java by SyncedFileState.kt Also fix some warning raised by AndroidStudio in affected class, fix some license header.

Technical details

As it is a central element of eDrive application, it has big impact on application's code. I tried to split implementation in many commit so it is easier to review.

Tests

Non regression test

Issues

None

One of my personnal goal (in the annual review scope) is to improve my kotlin skill by replacing java code from eDrive to kotlin code.

10 commandments of code reviews

👪 ❤ https://gitlab.e.foundation/internal/wiki/-/wikis/mobile-team/guidelines/Code-review

Summary by CodeRabbit

• New Features
  • Enhanced file synchronization handling with updated scannable states.
  • Introduced a new data model for managing synchronized file states.
• Bug Fixes
  • Improved error handling with null checks to prevent potential exceptions.
• Documentation
  • Updated method documentation for clarity on parameters and functionality.
• Refactor
  • Standardized naming conventions for constants and method calls across the codebase.
• Tests
  • Updated test cases to reflect changes in scannable state constants, ensuring accurate testing of synchronization logic.