[AL-2293] Support update_creds_key for existing creds

[FayazRahman]

🚀 🚀 Pull Request

Checklist:

• My code follows the style guidelines of this project and the Contributing document
• I have commented my code, particularly in hard-to-understand areas
• I have kept the coverage-rate up
• I have performed a self-review of my own code and resolved any problems
• I have checked to ensure there aren't any other open Pull Requests for the same change
• I have described and made corresponding changes to the relevant documentation
• New and existing unit tests pass locally with my changes

Changes

• Allow replacing creds key with existing creds key
• Only allowed if management status is the same

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.02 🎉

Comparison is base (f6d7f66) 84.70% compared to head (dedbf0d) 84.73%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2380      +/-   ##
==========================================
+ Coverage   84.70%   84.73%   +0.02%     
==========================================
  Files         326      326              
  Lines       37552    37616      +64     
==========================================
+ Hits        31810    31873      +63     
- Misses       5742     5743       +1     

Flag	Coverage Δ
unittests	84.73% <100.00%> (+0.02%)	⬆️

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

Impacted Files	Coverage Δ
deeplake/api/dataset.py	85.04% <ø> (+0.21%)	⬆️
deeplake/api/tests/test_link.py	98.34% <100.00%> (+0.34%)	⬆️
deeplake/core/dataset/dataset.py	91.27% <100.00%> (ø)
deeplake/core/dataset/deeplake_cloud_dataset.py	92.73% <100.00%> (+0.20%)	⬆️
deeplake/core/link_creds.py	92.27% <100.00%> (+0.45%)	⬆️
deeplake/util/link.py	98.11% <100.00%> (ø)

... and 9 files with indirect coverage changes

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