dvc: don't use realpath where not needed

[efiop]

On windows it will get resolved to a UNC path, which is very error prone.

We've been misusing realpath in some repo-related places that triggered the need to use it in other places.

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (ca0ad23) 90.46% compared to head (d9dfe26) 90.46%.

❗ Current head d9dfe26 differs from pull request most recent head 967d49a. Consider uploading reports for the commit 967d49a to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #9780   +/-   ##
=======================================
  Coverage   90.46%   90.46%           
=======================================
  Files         480      480           
  Lines       36602    36615   +13     
  Branches     5272     5277    +5     
=======================================
+ Hits        33112    33125   +13     
  Misses       2892     2892           
  Partials      598      598           

Files Changed	Coverage Δ
dvc/utils/__init__.py	68.88% <ø> (ø)
dvc/config.py	96.29% <100.00%> (ø)
dvc/exceptions.py	93.91% <100.00%> (+0.08%)	⬆️
dvc/repo/__init__.py	94.50% <100.00%> (ø)
dvc/repo/experiments/executor/base.py	80.56% <100.00%> (ø)
dvc/repo/graph.py	92.59% <100.00%> (+0.38%)	⬆️
dvc/repo/init.py	93.87% <100.00%> (ø)
dvc/repo/stage.py	94.44% <100.00%> (+0.12%)	⬆️
dvc/stage/utils.py	92.64% <100.00%> (ø)
tests/func/test_stage.py	100.00% <100.00%> (ø)
... and 1 more

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.