Several updates and fixes

- Removed all `thread::sleep` and use `tokio::time::sleep` now.
  This solves an issue with updating to Bullseye ( Resolves #1998 )
- Updated all Debian images to Bullseye
- Added MiMalloc feature and enabled it by default for Alpine based images
  This increases performance for the Alpine images because the default
  memory allocator for MUSL based binaries isn't that fast
- Updated `dotenv` to `dotenvy` a maintained and updated fork
- Fixed an issue with a newer jslib (not fully released yet)
  That version uses a different endpoint for `prelogin` Resolves #2378 )