refactor(railpack): extract static image build, fix port logic, bump to v0.22.0

Extract build_railpack_static_image() into its own method, prevent port
override when is_static is set, bump Railpack to 0.22.0, and improve
test setup with beforeEach and correct polymorphic env var fields.

app/Livewire/Project/New/PublicGitRepository.php

@@ -101,7 +101,9 @@ class PublicGitRepository extends Component
     {
         if ($this->build_pack === 'nixpacks' || $this->build_pack === 'railpack') {
             $this->show_is_static = true;
-            $this->port = 3000;
+            if (! $this->isStatic) {
+                $this->port = 3000;
+            }
         } elseif ($this->build_pack === 'static') {
             $this->show_is_static = false;
             $this->isStatic = false;