pageserver: fixes for layer path changes

[jcsp]

Problem

• When a layer with legacy local path format is evicted and then re-downloaded, a panic happened because the path downloaded by remote storage didn't match the path stored in Layer.
• While investigating, I also realized that secondary locations would have a similar issue with evictions.

Closes: #7783

Summary of changes

• Make remote timeline client take local paths as an input: it should not have its own ideas about local paths, instead it just uses the layer path that the Layer has.
• Make secondary state store an explicit local path, populated on scan of local disk at startup. This provides the same behavior as for Layer, that our local_layer_path is a default, but the layer path can actually be anything (e.g. an old style one).
• Add tests for both cases.

Checklist before requesting a review

• I have performed a self-review of my code.
• If it is a core feature, I have added thorough tests.
• Do we need to implement analytics? if so did you add the relevant metrics to the dashboard?
• If this PR requires public announcement, mark it with /release-notes label and add several sentences in this section.

Checklist before merging

• Do not forget to reformat commit message to not include the above checklist

[github-actions]

3066 tests run: 2939 passed, 0 failed, 127 skipped (full report)

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Code coverage* (full report)

• functions: 31.5% (6351 of 20188 functions)
• lines: 47.5% (47950 of 101051 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
4c516fa at 2024-05-17T09:21:38.768Z :recycle:}