Remove dvcignore reset in repo._reset

[karajan1001]

fix #3869
Repo add,checkout,etc will not change .dvcignore, and can remove dvcignore reset after these operations.

• ❗ 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. 🙏

No performance improvement in dvc status(only influence commands using repo._reset())

@pared Excuse me, my dvc add tests failed.
On origin/master, clone the local repo to ./ then edit hashes.txt manually and run asv run HASHFILE:hashes.txt. And these is my error message.

[pared]

@karajan1001
You need to pull the cats_dogs data from public repo, it should be configured inside repo. Please run:
dvc pull data/cats_dogs.dvc -r bench_s3_public

EDIT:
updated README: treeverse/dvc-bench#200

[skshetry]

@karajan1001, one test is failing, need adjustment on:
https://github.com/iterative/dvc/blob/78458ee5a1f5d4423340494e0d25b24551e48748/tests/func/test_tree.py#L260

Just need to call after that location dvc_tree.__dict__.pop("dvcignore", None).

[codecov]

Codecov Report

Merging #4371 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #4371   +/-   ##
=======================================
  Coverage   90.92%   90.92%           
=======================================
  Files         178      178           
  Lines       12352    12352           
=======================================
  Hits        11231    11231           
  Misses       1121     1121           

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[skshetry]

Feels like we need tree._reset() kind of API anyway for the tests. Though, looks good for now.