[CLD-6894] Add 60, 30, and 7 day reminder emails for Cloud Renewals (#25883)

* Add email notifications for Cloud Renewals

* Updates

* Updates

* Update app-layers

* make build-templates

* Add ability to set an env variable as a unix timestamp in s as the current date when getting DaysToExpiration

* Add a mechanism to ensure at least one admin receives every email

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Co-authored-by: Mattermost Build <build@mattermost.com>
Co-authored-by: Gabe Jackson <3694686+gabrieljackson@users.noreply.github.com>

webapp/channels/webpack.config.js

@@ -191,6 +191,8 @@ var config = {
                 {from: 'src/images/cloud-laptop-error.png', to: 'images'},
                 {from: 'src/images/cloud-laptop-warning.png', to: 'images'},
                 {from: 'src/images/cloud-upgrade-person-hand-to-face.png', to: 'images'},
+                {from: 'src/images/payment_processing.png', to: 'images'},
+                {from: 'src/images/purchase_alert.png', to: 'images'},
                 {from: '../node_modules/pdfjs-dist/cmaps', to: 'cmaps'},
             ],
         }),