Migrate modals and popovers from Django templates to Handlebars

We have a bundle of small overlays, modals and popovers in templates/zerver/app that we should migrate to a handlebars template as part of #18792. This issue lays out the plan for doing so, in terms of new filenames (often clearer)

• lightbox_overlay.html => lightbox_overlay.hbs. This should be straightforward as there are no conditionals; we just need to migrate translation tags.
• index.html has the user_status_overlay, aka the right sidebar “set my status” overlay, embedded in it. We should extract that as set_status_overlay.hbs. This should be straightforward; we just need to migrate translation tags.
• message_history.html. Accessible by hitting the “Show edit history” option in the message actions menu after editing a message. It’s a simple modal with just a “Close” button and migration should mostly just involve translation tag changes.
• about-zulip.html => static/templates/about_zulip.hbs. Requires moving the two variables it uses to page_params from the context as discussed in #18792, but should be otherwise straightforward. Accessible in the gear menu as “About Zulip” for testing.
• deprecation_notice.html => static/templates/deprecated_feature_notice.hbs. Should just require moving code and editing translation tags, but we might want to move the JavaScript code to deprecated_feature_notice.js and migrate the variable names in the same PR. Accessible by hitting the * or C hotkey.
• invite_user.html => static/templates/invite_users.hbs. This one may be a bit involved of a migration, since we have various role data fields in here. @sahil839 would you be up for taking this one? (Feel free to grab any others as well).

I’d appreciate each of these migrations being independent small PRs (possibly with extra commits to clean up related variable names for consistency). So folks should claim individual items via comments here, not claiming the whole issue.

[ganpa3]

I am taking up invite users modal part.

Great. I will grab the rest.

[sahil839]

I am taking up invite users modal part.