refactor(tvix/store/fs): Decouple TvixStoreFs from Nix concepts r/7222

To support tvix builds, we need to be able to use the `TvixStoreFs` to
materialize the sandbox's /nix/store filesystem with just the list of
inputs needed for the build. Currently we'd need to seed an in-memory
`PathInfoService`, which includes more functionality than what is
required for `TvixStoreFs`. Additionally, the `PathInfoService` is
specific to Nix. By decoupling `TvixStoreFs` and `PathInfoService`,
we allow for usage of `TvixStoreFs` with `tvix-castore` without needing
a `PathInfoService`.

This introduces a new `RootNodes` trait which provides a way for the
filesystem to look up CA nodes via their basename in the root directory
of the filesystem. We then implement `RootNodes` for any
`PathInfoService`. Additionally, the filesystem root inode tracker now
stores basenames rather than `StorePath`s since `StorePath`s are
specific to Nix.

As a followup we can rename `TvixStoreFs` to `TvixCaStoreFs` and move
it to the `castore` crate (or its own crate).

b/341

Change-Id: I928372955017c23b1bf2b37190cbc508a4ed10d5
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10363
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>

0 files changed, 0 insertions, 0 deletions