Edit UI: create new FF to enable restorations per entity types

Currently there is a flag, `restoration-ui-enabled`, that controls whether restoration filings are enabled (in Dev/Test/Prod).

Instead, we should have a flag for this filing that controls which entities are allowed.

See #15734 for more details.

- [x] create new flag in LD -> `supported-restoration-entities`
- [ ] add check in Filings UI for starting a restoration (there may be an existing ticket from Riyaz)
- [ ] delete current flag in code (and its usage)
- [ ] create new flag in code (and its usage)
- [ ] archive (delete) the old flag in LD (add this to release ticket)

Start with the details in #15734 and locate the Filings UI flow for starting a restoration, including the existing restoration-ui-enabled usage. Trace the checklist through the new supported-restoration-entities flag, the UI check, old-flag removal, and the release ticket; done means the new flag controls allowed entity types and the old flag is removed and archived.

Written by the indexing model from the issue text.