fs: get_cloud_fs: accept config instead of repo

[efiop]

Config is a more immutable thing and using repo is confusing and might be error prone in the bigger picture.

Related/pre-requisite to #9754

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.27% ⚠️

Comparison is base (7806afd) 90.47% compared to head (6b587ec) 90.20%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9755      +/-   ##
==========================================
- Coverage   90.47%   90.20%   -0.27%     
==========================================
  Files         480      480              
  Lines       36595    36588       -7     
  Branches     5264     5263       -1     
==========================================
- Hits        33108    33003     -105     
- Misses       2889     2964      +75     
- Partials      598      621      +23     

Files Changed	Coverage Δ
dvc/cachemgr.py	73.68% <100.00%> (ø)
dvc/data_cloud.py	68.18% <100.00%> (ø)
dvc/fs/__init__.py	100.00% <100.00%> (ø)
dvc/output.py	84.26% <100.00%> (ø)
tests/unit/fs/test_fs.py	93.33% <100.00%> (-0.96%)	⬇️
tests/unit/fs/test_tree.py	100.00% <100.00%> (ø)
tests/unit/remote/test_remote.py	100.00% <100.00%> (ø)
tests/unit/remote/test_webdav.py	100.00% <100.00%> (ø)

... and 26 files with indirect coverage changes

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