[MM-55341][MM-56894] Use electron-builder to create the MSI installer, drop support for 32-bit Windows and the NSIS installer (#3028)

* Drop 32-bit windows support

* Remove unnecessary after build script

* Enable MSI build from electron-builder

* Copy MSI installers correctly

* Change script to `windows-installer`

* Revert "Remove unnecessary after build script"

This reverts commit 65b1cccb063656916a7d12c440792ad013dff826.

* Fix duplicate installers when updating to EXE version

* Inject the app-update.yml from the NSIS installer into the MSI, have the MSI uninstall the EXE if it exists

* Cleanup old MSI builder, switch actions to use new process

* Sign PR builds

* Update to use absolute paths

* Use env variable paths

scripts/cp_msi_app_update.js

@@ -0,0 +1,6 @@
+// Copyright (c) 2016-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+const fs = require('fs');
+fs.copyFileSync('release/win-unpacked/resources/app-update.yml', 'release/msi-app-update.yml');
+fs.unlinkSync('release/win-unpacked/resources/app-update.yml');