Turbopack: add more context to persistence file errors (#95318)
### What?
Adds path- and operation-level context to the filesystem errors raised
by the `turbo-persistence` commit/rollback flow and the
`turbo-tasks-backend` database invalidation/versioning helpers.
### Why?
A user reported a bare `Access is denied. (OS error 5)` on Windows 11
that surfaced out of the cache `commit` flow with no indication of which
file or which filesystem operation failed:
https://github.com/vercel/next.js/discussions/95130#discussioncomment-17479429
The underlying issue was fixed in #95495 but this adds more information
for future issues.
Raw `io::Error`s from `?` carry an OS error code but no path, so there
was no way to tell whether the failure was on `CURRENT`, a `.del` file,
a per-file `fsync`, the directory `fsync`, or a cleanup `remove_file`
etc.
### How?
- Adopted the `fs_err` crate for all fs operations in the persistence
layer
- Added additional context to some flows
- Unified `CURRENT` file writing and adopted an 'atomic write' pattern.
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