Replace Prefire with a very similar but simpler and more direct approach (#3232)

* Replace Prefire with a very similar but simpler and more direct approach

* Move PreviewTest snapshots to their new location (snapshotting default, mirrors UITests)

* Update acknowledgements

* Switch snapshot configuration extensions to a custom version

* Exclude snapshots from the PreviewTests target

* Fix acknowledgements

* Rename snapshotting preference keys

* Remove `skipPackagePluginValidation`

ElementX/SupportingFiles/target.yml

@@ -139,14 +139,26 @@ targets:
         else
             echo "warning: SwiftGen not installed, download from https://github.com/SwiftGen/SwiftGen"
         fi
-    - name: 🧙 Sourcery
+    - name: 🧙 Sourcery - Generate mocks
       runOnlyWhenInstalling: false
       basedOnDependencyAnalysis: false
       shell: /bin/sh
       script: |
         export PATH="$PATH:/opt/homebrew/bin"
         if which sourcery >/dev/null; then
-            sourcery --config Tools/Sourcery/sourcery_automockable_config.yml
+            sourcery --config Tools/Sourcery/AutoMockableConfig.yml
+        else
+            echo "warning: Sourcery not installed, run swift run tools setup-project"
+        fi
+
+    - name: 🧙 Sourcery - Generate preview tests
+      runOnlyWhenInstalling: false
+      basedOnDependencyAnalysis: false
+      shell: /bin/sh
+      script: |
+        export PATH="$PATH:/opt/homebrew/bin"
+        if which sourcery >/dev/null; then
+            sourcery --config Tools/Sourcery/PreviewTestsConfig.yml
         else
             echo "warning: Sourcery not installed, run swift run tools setup-project"
         fi
@@ -202,7 +214,6 @@ targets:
     - package: Version
     - package: Emojibase
     - package: WysiwygComposer
-    - package: Prefire
     - package: SwiftOGG
     - package: DSWaveformImage
       product: DSWaveformImageViews