release-24.1: storage: fix cases of unencoded key ranges

[RaduBerinde]

Backport 1/1 commits from #128816.

/cc @cockroachdb/release

---

This is a backport of the fixes inside #128043. These are a few cases where we are passing unencoded key ranges to Pebble for various operations. This can result in an effective range that starts and/or ends sooner than intended (part of the key will be treated as the suffix).

Release justification: fix for Online Restore download phase and for key range table metrics.

Epic: none
Release note: None

[blathers-crl]

Thanks for opening a backport.

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[blathers-crl]

It looks like your PR touches production code but doesn't add or edit any test code. Did you consider adding tests to your PR?

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[cockroach-teamcity]

This change is