Explode drupal/core-dev require-dev dependency into the minimum packages we need.

The drupal/core-dev package is simply a shortcut for including
dependencies necessary for running automated tests.
See https://github.com/drupal/core-dev/blob/9.4.x/composer.json

It is designed specifically for running Drupal core automated
tests. We used it as a simple way to get our automated tests
running initially, but it includes some dependencies that we do
not need.

It also pins some package versions, including symfony/finder and
symfony/filesystem. This caused an issue for us when we refactored
our composer.json files to use composer-merge-plugin. We got
around this issue by pinning symfony/finder to ^4.

See https://www.drupal.org/project/farm/issues/3239420
See bd33d0f139

Furthermore, in testing Drush 11, I discovered that a similar
conflict started occurring with symfony/filesystem (presumably
because Drush depends on that as well now). I eventually managed
to get it to work by pinning symfony/filesystem as well, but only
if I moved both pins to the root farmOS composer.json (it didn't
fix it if they were in composer.project.json). That is what
ultimately drove me to dig into this and decide to split up our
dependency on drupal/core-dev.

By removing the dependency on drupal/core-dev, we no longer have
the issue with symfony/finder, so that pinned dependency can
be removed.

I repeatedly ran tests with as few of the drupal/core-dev
dependencies as possible until tests started passing again. So
this final list represents the minimum requirements for our
tests.

composer.project.json

@@ -4,18 +4,22 @@
         "drupal/core-composer-scaffold": "9.4.8"
     },
     "require-dev": {
+        "behat/mink": "^1.10",
+        "behat/mink-selenium2-driver": "^1.6",
         "brianium/paratest": "^4",
-        "drupal/core-dev": "9.4.8",
+        "drupal/coder": "^8.3",
+        "friends-of-behat/mink-browserkit-driver": "^1.6",
         "mglaman/phpstan-drupal": "^1.1",
+        "mikey179/vfsstream": "^1.6",
         "phpstan/extension-installer": "^1.1",
         "phpcompatibility/php-compatibility": "^9",
         "phpstan/phpstan": "^1.8",
         "phpstan/phpstan-deprecation-rules": "^1.0",
+        "phpunit/phpunit": "^9",
         "phpspec/prophecy-phpunit": "^2",
-        "symfony/finder": "^4.0"
+        "symfony/phpunit-bridge": "^5.4"
     },
     "_comments": {
-        "symfony/finder": "Required to pin v4, otherwise composer-merge-plugin causes problem: package is fixed to v5.3.7 (lock file version) by a partial update",
         "phpspec/prophecy-phpunit": "Required to fix ProphecyTrait not found, until Drupal core drops support for PHPUnit 8. See https://www.drupal.org/node/3176567"
     },
     "conflict": {