import: error out on import from cloud-versioned remote

[pmrowla]

• ❗ I have followed the Contributing to DVC checklist.

• 📖 If this PR requires documentation updates, I have created a separate PR (or issue, at least) in dvc.org and linked it here.

Thank you for the contribution - we'll try to review it as soon as possible. 🙏

Related: #8789

Exception will now be raised when importing a file from a DVC repo that would require cloud-versioned remotes.

$ dvc import ../scratch/cloud-versioning cats-dogs
Importing 'cats-dogs (../scratch/cloud-versioning)' -> 'cats-dogs'
ERROR: failed to import 'cats-dogs' from '../scratch/cloud-versioning'. - Target repository '../scratch/cloud-versioning' uses cloud-versioned remotes.: 'dvc import' is unsupported for cloud versioned remotes

[pmrowla]

The error message ends up being a bit verbose due to the exception chaining (it gets nested inside the general import error, then the general erepo error) but should be good enough for now.

[codecov]

Codecov Report

Patch coverage: 78.57% and project coverage change: -0.02 ⚠️

Comparison is base (c8745dd) 92.91% compared to head (c921972) 92.90%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9182      +/-   ##
==========================================
- Coverage   92.91%   92.90%   -0.02%     
==========================================
  Files         456      456              
  Lines       36869    36888      +19     
  Branches     5322     5326       +4     
==========================================
+ Hits        34258    34269      +11     
- Misses       2087     2092       +5     
- Partials      524      527       +3     

Impacted Files	Coverage Δ
dvc/data_cloud.py	82.19% <50.00%> (ø)
dvc/config.py	98.04% <66.66%> (-0.47%)	⬇️
dvc/exceptions.py	95.07% <66.66%> (-0.62%)	⬇️
dvc/dependency/repo.py	92.95% <80.95%> (-2.57%)	⬇️
dvc/external_repo.py	81.17% <83.33%> (-0.65%)	⬇️
dvc/output.py	88.67% <100.00%> (ø)

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[efiop]

#9181 introduces index support for repo imports including cloud versioned stuff and cycles. The obj-related code probably will get removed and we would use fs directly like we do with regular import-urls.

[efiop]

@pmrowla Sorry for wasting your time on this, meant to discuss it today. 🙁