Allow passing [] and {} as argument.

[superstar54]

Fix a couple of bugs:

• Add merge_dict function to merge dict correctly
• Reset child tasks for Zone task
• Skip running task if the task is in SKIPPED state

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 84.61538% with 4 lines in your changes missing coverage. Please review.

Project coverage is 80.62%. Comparing base (5937b88) to head (4260f2d).
Report is 77 commits behind head on main.

Files with missing lines	Patch %	Lines
aiida_workgraph/engine/workgraph.py	66.66%	2 Missing ⚠️
aiida_workgraph/utils/__init__.py	88.23%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #328      +/-   ##
==========================================
+ Coverage   75.75%   80.62%   +4.87%     
==========================================
  Files          70       66       -4     
  Lines        4615     5147     +532     
==========================================
+ Hits         3496     4150     +654     
+ Misses       1119      997     -122     

Flag	Coverage Δ
python-3.11	80.55% <84.61%> (+4.88%)	⬆️
python-3.12	80.55% <84.61%> (?)
python-3.9	80.58% <84.61%> (+4.84%)	⬆️

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