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, 87 deletions

diff --git a/tests/flakes/init.sh b/tests/flakes/init.sh
deleted file mode 100644
index 2d4c77ba1..000000000
--- a/tests/flakes/init.sh
+++ /dev/null
@@ -1,87 +0,0 @@
-source ./common.sh
-
-requireGit
-
-templatesDir=$TEST_ROOT/templates
-flakeDir=$TEST_ROOT/flake
-nixpkgsDir=$TEST_ROOT/nixpkgs
-
-nix registry add --registry $registry templates git+file://$templatesDir
-nix registry add --registry $registry nixpkgs git+file://$nixpkgsDir
-
-createGitRepo $nixpkgsDir
-createSimpleGitFlake $nixpkgsDir
-
-# Test 'nix flake init'.
-createGitRepo $templatesDir
-
-cat > $templatesDir/flake.nix <<EOF
-{
-  description = "Some templates";
-
-  outputs = { self }: {
-    templates = rec {
-      trivial = {
-        path = ./trivial;
-        description = "A trivial flake";
-        welcomeText = ''
-            Welcome to my trivial flake
-        '';
-      };
-      default = trivial;
-    };
-  };
-}
-EOF
-
-mkdir $templatesDir/trivial
-
-cat > $templatesDir/trivial/flake.nix <<EOF
-{
-  description = "A flake for building Hello World";
-
-  outputs = { self, nixpkgs }: {
-    packages.$system = rec {
-      hello = nixpkgs.legacyPackages.$system.hello;
-      default = hello;
-    };
-  };
-}
-EOF
-echo a > $templatesDir/trivial/a
-echo b > $templatesDir/trivial/b
-
-git -C $templatesDir add flake.nix trivial/
-git -C $templatesDir commit -m 'Initial'
-
-nix flake check templates
-nix flake show templates
-nix flake show templates --json | jq
-
-createGitRepo $flakeDir
-(cd $flakeDir && nix flake init)
-(cd $flakeDir && nix flake init) # check idempotence
-git -C $flakeDir add flake.nix
-nix flake check $flakeDir
-nix flake show $flakeDir
-nix flake show $flakeDir --json | jq
-git -C $flakeDir commit -a -m 'Initial'
-
-# Test 'nix flake init' with benign conflicts
-createGitRepo "$flakeDir"
-echo a > $flakeDir/a
-(cd $flakeDir && nix flake init) # check idempotence
-
-# Test 'nix flake init' with conflicts
-createGitRepo "$flakeDir"
-echo b > $flakeDir/a
-pushd $flakeDir
-(! nix flake init) |& grep "refusing to overwrite existing file '$flakeDir/a'"
-popd
-git -C $flakeDir commit -a -m 'Changed'
-
-# Test 'nix flake new'.
-rm -rf $flakeDir
-nix flake new -t templates#trivial $flakeDir
-nix flake new -t templates#trivial $flakeDir # check idempotence
-nix flake check $flakeDir