Implement fsync for delete operations in local.rs

> WHy doesn't fsync apply to standalone deletes (if we don't fsync isn't there some chance that a deleted file will get "undeleted" on crash)?

it should! but it doesnt right now, the documented mentions only write-like operations and not deletes
https://github.com/apache/arrow-rs-object-store/blob/c9db3e22d2eed690b7a9c14a988ec85d6b9304ad/src/local.rs#L310-L316

Let's do a follow up to make standalone `delete` / `delete_stream` crash-durable

_Originally posted by @kevinjqliu in https://github.com/apache/arrow-rs-object-store/pull/758#discussion_r3436778013_

Start in src/local.rs at the documented fsync behavior around lines 310–316, then trace the standalone delete and delete_stream entry points. Confirm how existing write-like operations make changes durable and extend the delete paths so standalone deletions are crash-durable; done means both operations follow the intended fsync behavior.

Written by the indexing model from the issue text.