## Problem
The storage components take an entire `SafekeeperConf` during
construction, but only actually use the `no_sync` field. This makes it
hard to understand the storage inputs (which fields do they actually
care about?), and is also inconvenient for tests and benchmarks that
need to set up a lot of unnecessary boilerplate.
## Summary of changes
* Don't take the entire config, but pass in the `no_sync` field
explicitly.
* Take the timeline dir instead of `ttid` as an input, since it's the
only thing it cares about.
* Fix a couple of tests to not leak tempdirs.
* Various minor tweaks.
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