Add class reordering in dataset

[sokovninn]

Purpose

Adds class reordering functionality to the LuxonisDataset to allow users to specify custom class ordering for tasks. This enables control over class-to-index mapping which is important for model consistency and deployment scenarios where specific class ordering is required.

Specification

• Implemented set_class_order_per_task() method with validation:
  • Checks if task names exist in dataset
  • Validates that provided classes match dataset classes exactly
  • Only reorders when class order differs from current order
  • Provides clear warning messages when reordering occurs
• Class reordering doesn't update dataset metadata on disk

Dependencies & Potential Impact

None / not applicable

Deployment Plan

None / not applicable

Testing & Validation

None / not applicable

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.30%. Comparing base (ab8709e) to head (70d777d).
⚠️ Report is 5 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #351      +/-   ##
==========================================
+ Coverage   95.29%   95.30%   +0.01%     
==========================================
  Files         103      103              
  Lines        6328     6386      +58     
==========================================
+ Hits         6030     6086      +56     
- Misses        298      300       +2     

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[klemen1999]

LGTM but let's add some tests for it please