R1:afa69eedd1a5

Remove an old digest in Celerity code and some obsolete configuration options

Summary:
Ref T12509. This upgrades a `weakDigest()` callsite to SHA256-HMAC and removes three config options:

- `celerity.resource-hash`: Now hard-coded, since the use case for ever adjusting it was very weak.
- `celerity.enable-deflate`: Intended to make cache inspection easier, but we haven't needed to inspect caches in ~forever.
- `celerity.minify`: Intended to make debugging minification easier, but we haven't needed…