ci: Split mainline pipeline and add support for GitHub releases (#2900)

* ci: Add mock build alternative for fast testing

* ci: Always cache build

* ci: Extract steps to download build stage artifacts

* ci: Add template to release to GitHub

* ci: Add template to release to Azure Universal Artifacts

* ci: Split mainline to two pipelines

.ci/templates/release-universal.yml

@@ -0,0 +1,10 @@
+steps:
+  - template: ./release-download.yml
+  - task: UniversalPackages@0
+    displayName: Publish Artifacts
+    inputs:
+      command: publish
+      publishDirectory: '$(Build.ArtifactStagingDirectory)'
+      vstsFeedPublish: 'yuzu-$(BuildName)'
+      vstsFeedPackagePublish: 'main'
+      packagePublishDescription: 'Yuzu Windows and Linux Executable Packages'