[AL-2372] do not accept empty tokens for private datasets

[levongh]

🚀 🚀 Pull Request

Impact

• Bug fix (non-breaking change which fixes expected existing functionality)
• Enhancement/New feature (adds functionality without impacting existing logic)
• Breaking change (fix or feature that would cause existing functionality to change)

Description

if the dataset's token is empty or None and the dataset is not a public one then we need to get the token from the client side to normally process and create dataloader object from it

Things to be aware of

Things to worry about

Additional Context

[codecov]

Codecov Report

Patch coverage: 33.33% and project coverage change: +0.01% 🎉

Comparison is base (fe1a109) 84.90% compared to head (9fed361) 84.92%.
Report is 6 commits behind head on main.

❗ Current head 9fed361 differs from pull request most recent head 360198f. Consider uploading reports for the commit 360198f to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2507      +/-   ##
==========================================
+ Coverage   84.90%   84.92%   +0.01%     
==========================================
  Files         328      328              
  Lines       38830    38820      -10     
==========================================
- Hits        32970    32968       -2     
+ Misses       5860     5852       -8     

Flag	Coverage Δ
unittests	84.92% <33.33%> (+0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
...lake/core/vectorstore/test_deeplake_vectorstore.py	59.91% <ø> (+0.12%)	⬆️
deeplake/core/tests/test_deeplake_indra_dataset.py	12.30% <33.33%> (+1.05%)	⬆️
deeplake/enterprise/convert_to_libdeeplake.py	50.00% <33.33%> (+5.14%)	⬆️

... and 12 files with indirect coverage changes

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