[FIX] Ensure unlockable sparse arrays after Table.copy

[markotoplak]

Issue

Fixes #5746

Includes

• Code changes
• Tests
• Documentation

[codecov]

Codecov Report

Merging #5807 (2b0cd0c) into master (172b33d) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #5807      +/-   ##
==========================================
- Coverage   86.14%   86.14%   -0.01%     
==========================================
  Files         316      316              
  Lines       66417    66419       +2     
==========================================
- Hits        57217    57215       -2     
- Misses       9200     9204       +4     

[PrimozGodec]

Tests are fixed in #5822

So if I understand correct @markotoplak:

from Orange.data import Table

Table.LOCKING = True
data = Table("zoo")
data = data.to_sparse()
with data.unlocked():  <-- this should still fail since to_sparse use transform and data can be a view
    pass

with data.copy().unlocked():  <-- this does not fail anymore
    pass

[markotoplak]

@PrimozGodec, yes, you are correct.