Wrap rest functions with `computed`

Probably out of scope for this PR, but we could probably just import `computed` in `rest.ts` and define these as `computed(() => ...)` instead of `() => ...`, which saves you having to do this song and dance in every component that needs to use them.

_Originally posted by @dchiquito in https://github.com/dandi/dandiarchive/pull/901#discussion_r717847282_

Start by locating rest.ts and reading the functions referenced as “these,” then inspect the components that currently consume them. Confirm how the functions are used and whether existing tests cover them; done means the rest functions use computed as proposed and their consumers still work.

Written by the indexing model from the issue text.