checkout/pull: dvcignored contents are removed on checkout

[skshetry]

cd "$(mktemp -d)"
dvc init --no-scm
dvc remote add -d local "$(mktemp -d)"
mkdir -p data/processed
echo "foo" > data/foo
echo "bar" > data/processed/bar
echo "data/processed/" >> .dvcignore
dvc add data
dvc push
rm -rf .dvc/cache data/foo
dvc pull | tee

This is a regression introduced in b349b39 (see #5812), which was released in 2.2.0 and is present since then.

[skshetry]

#4344 and this issue are related to staging in dvc-data.