move `formatDate` from ui/helpers/utils/util.js to `shared`, and standardize its usage

[danjm]

We have a formatDate method in ui/helpers/utils/util.js. We also have one in shared/notifications/index.ts. As of https://github.com/MetaMask/metamask-extension/pull/24503, we also have one in app/scripts/controllers/metametrics-data-deletion/metametrics-data-deletion.ts

We should create one standard formatDate method that is used throughout the codebase.