Put functional tests in `tests/functional`

I think it is bad for these reasons when `tests/` contains a mix of
functional and integration tests

 - Concepts is harder to understand, the documentation makes a good
   unit vs functional vs integration distinction, but when the
   integration tests are just two subdirs within `tests/` this is not
   clear.

 - Source filtering in the `flake.nix` is more complex. We need to
   filter out some of the dirs from `tests/`, rather than simply pick
   the dirs we want and take all of them. This is a good sign the
   structure of what we are trying to do is not matching the structure
   of the files.

With this change we have a clean:
```shell-session
$ git show 'HEAD:tests'
tree HEAD:tests

functional/
installer/
nixos/
```

(cherry picked from commit 68c81c737571794f7246db53fb4774e94fcf4b7e)

1 files changed, 0 insertions, 106 deletions

diff --git a/tests/fetchMercurial.sh b/tests/fetchMercurial.sh
deleted file mode 100644
index e6f8525c6..000000000
--- a/tests/fetchMercurial.sh
+++ /dev/null
@@ -1,106 +0,0 @@
-source common.sh
-
-[[ $(type -p hq) ]] || skipTest "Mercurial not installed"
-
-clearStore
-
-# Intentionally not in a canonical form
-# See https://github.com/NixOS/nix/issues/6195
-repo=$TEST_ROOT/./hg
-
-rm -rf $repo ${repo}-tmp $TEST_HOME/.cache/nix
-
-hg init $repo
-echo '[ui]' >> $repo/.hg/hgrc
-echo 'username = Foobar <foobar@example.org>' >> $repo/.hg/hgrc
-
-# Set ui.tweakdefaults to ensure HGPLAIN is being set.
-echo 'tweakdefaults = True' >> $repo/.hg/hgrc
-
-echo utrecht > $repo/hello
-touch $repo/.hgignore
-hg add --cwd $repo hello .hgignore
-hg commit --cwd $repo -m 'Bla1'
-rev1=$(hg log --cwd $repo -r tip --template '{node}')
-
-echo world > $repo/hello
-hg commit --cwd $repo -m 'Bla2'
-rev2=$(hg log --cwd $repo -r tip --template '{node}')
-
-# Fetch an unclean branch.
-echo unclean > $repo/hello
-path=$(nix eval --impure --raw --expr "(builtins.fetchMercurial file://$repo).outPath")
-[[ $(cat $path/hello) = unclean ]]
-hg revert --cwd $repo --all
-
-# Fetch the default branch.
-path=$(nix eval --impure --raw --expr "(builtins.fetchMercurial file://$repo).outPath")
-[[ $(cat $path/hello) = world ]]
-
-# In pure eval mode, fetchGit without a revision should fail.
-[[ $(nix eval --impure --raw --expr "(builtins.readFile (fetchMercurial file://$repo + \"/hello\"))") = world ]]
-(! nix eval --raw --expr "builtins.readFile (fetchMercurial file://$repo + \"/hello\")")
-
-# Fetch using an explicit revision hash.
-path2=$(nix eval --impure --raw --expr "(builtins.fetchMercurial { url = file://$repo; rev = \"$rev2\"; }).outPath")
-[[ $path = $path2 ]]
-
-# In pure eval mode, fetchGit with a revision should succeed.
-[[ $(nix eval --raw --expr "builtins.readFile (fetchMercurial { url = file://$repo; rev = \"$rev2\"; } + \"/hello\")") = world ]]
-
-# Fetch again. This should be cached.
-mv $repo ${repo}-tmp
-path2=$(nix eval --impure --raw --expr "(builtins.fetchMercurial file://$repo).outPath")
-[[ $path = $path2 ]]
-
-[[ $(nix eval --impure --raw --expr "(builtins.fetchMercurial file://$repo).branch") = default ]]
-[[ $(nix eval --impure --expr "(builtins.fetchMercurial file://$repo).revCount") = 1 ]]
-[[ $(nix eval --impure --raw --expr "(builtins.fetchMercurial file://$repo).rev") = $rev2 ]]
-
-# But with TTL 0, it should fail.
-(! nix eval --impure --refresh --expr "builtins.fetchMercurial file://$repo")
-
-# Fetching with a explicit hash should succeed.
-path2=$(nix eval --refresh --raw --expr "(builtins.fetchMercurial { url = file://$repo; rev = \"$rev2\"; }).outPath")
-[[ $path = $path2 ]]
-
-path2=$(nix eval --refresh --raw --expr "(builtins.fetchMercurial { url = file://$repo; rev = \"$rev1\"; }).outPath")
-[[ $(cat $path2/hello) = utrecht ]]
-
-mv ${repo}-tmp $repo
-
-# Using a clean working tree should produce the same result.
-path2=$(nix eval --impure --raw --expr "(builtins.fetchMercurial $repo).outPath")
-[[ $path = $path2 ]]
-
-# Using an unclean tree should yield the tracked but uncommitted changes.
-mkdir $repo/dir1 $repo/dir2
-echo foo > $repo/dir1/foo
-echo bar > $repo/bar
-echo bar > $repo/dir2/bar
-hg add --cwd $repo dir1/foo
-hg rm --cwd $repo hello
-
-path2=$(nix eval --impure --raw --expr "(builtins.fetchMercurial $repo).outPath")
-[ ! -e $path2/hello ]
-[ ! -e $path2/bar ]
-[ ! -e $path2/dir2/bar ]
-[ ! -e $path2/.hg ]
-[[ $(cat $path2/dir1/foo) = foo ]]
-
-[[ $(nix eval --impure --raw --expr "(builtins.fetchMercurial $repo).rev") = 0000000000000000000000000000000000000000 ]]
-
-# ... unless we're using an explicit ref.
-path3=$(nix eval --impure --raw --expr "(builtins.fetchMercurial { url = $repo; rev = \"default\"; }).outPath")
-[[ $path = $path3 ]]
-
-# Committing should not affect the store path.
-hg commit --cwd $repo -m 'Bla3'
-
-path4=$(nix eval --impure --refresh --raw --expr "(builtins.fetchMercurial file://$repo).outPath")
-[[ $path2 = $path4 ]]
-
-echo paris > $repo/hello
-# Passing a `name` argument should be reflected in the output path
-path5=$(nix eval -vvvvv --impure --refresh --raw --expr "(builtins.fetchMercurial { url = \"file://$repo\"; name = \"foo\"; } ).outPath")
-[[ $path5 =~ -foo$ ]]