feat: support update and redownload of individual items

[swarnimarun]

Feature:

Now we can just do a redownload and it should internally verify a url based checksum(generated after first download), to see if the local files are stale and overwrite them if they are deemed to be so.

It also provides a command to directly invoke a from JS to check if the service is out of date(is_updated), for building user convenient interfaces.

Key Benefit

If just the binaries are outdated, the user won't have to delete and reinstall the entire service(weights included which can be huge).

Notes: The PR is ready but would need some gitfu to deal with the fact that it's showing more commits than what exist within the PR here... I blame github. :3

This partially,
Fixes #434

[swarnimarun]

closing pr will redo in a separate PR, rebasing it is way more annoying than I expected.