Default empty task name

[kozlov721]

Changed the default task_name from "detection" to an empty string. "detection" can be confusing for example for semantic segmentation tasks and there's not a reason to have any task name for datasets with only one task.

[klemen1999]

LGTM, just needs fixing of tests

[codecov]

Codecov Report

Attention: Patch coverage is 96.29630% with 1 line in your changes missing coverage. Please review.

Project coverage is 95.92%. Comparing base (539fde4) to head (4eabba5).
Report is 1 commits behind head on main.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
luxonis_ml/data/parsers/base_parser.py	92.85%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##           main     #222       +/-   ##
=========================================
+ Coverage      0   95.92%   +95.92%     
=========================================
  Files         0       88       +88     
  Lines         0     4737     +4737     
=========================================
+ Hits          0     4544     +4544     
- Misses        0      193      +193     

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