[FIX] Orange.data.Table: deprecated is_view and is_copy

[noahnovsak]

Issue

fixes #5878

Description of changes

deprecated is_view and is_copy as requested

Includes

• Code changes
• Tests

[codecov]

Codecov Report

Merging #5913 (f5cae57) into master (93cf05f) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head f5cae57 differs from pull request most recent head 6052878. Consider uploading reports for the commit 6052878 to get more accurate results

@@           Coverage Diff           @@
##           master    #5913   +/-   ##
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  Coverage   86.28%   86.28%           
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  Files         315      315           
  Lines       66833    66886   +53     
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+ Hits        57666    57712   +46     
- Misses       9167     9174    +7     

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[markotoplak]

@needNewUsername, thanks. The deprecations should also somehow notify the user what to do instead (I think this is a parameter to the decorator). Ideally, they would also specify when does the support stop.

And finally, make a time bomb that notifies us when to remove the code, like test_check_learner_adequacy_deprecated in #5848.

[markotoplak]

Thanks! Could you now rebase into a single commit?