pageserver: remove TenantConfOpt::TryFrom<toml_edit::Item>

[erikgrinaker]

Problem

Following #7656, TenantConfOpt::TryFrom<toml_edit::Item> appears to be dead code.

Resolves #8918.

Summary of changes

Remove TenantConfOpt::TryFrom<toml_edit::Item>.

The code does appear to be dead, since the TOML config is deserialized into TenantConfig (via LocationConfig) and then converted into TenantConfOpt.

This was verified by adding a panic to try_from() and running the pageserver unit tests as well as a local end-to-end cluster (including creating a new tenant and restarting the pageserver). This did not fail, so this is not used on the common happy path at least. No explicit try_from or try_into calls were found either.

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

[erikgrinaker]

@koivunej Christian is busy, perhaps you can review this instead since you were also involved on #7656?

[github-actions]

5022 tests run: 4864 passed, 0 failed, 158 skipped (full report)

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Flaky tests (6)

Postgres 17

• test_pageserver_compaction_smoke: release-arm64
• test_restart_endpoint_after_switch_wal: release-x86-64, debug-x86-64

Postgres 16

• test_obsolete_slot_drop[cross-validation]: release-x86-64
• test_slots_and_branching: release-x86-64

Postgres 14

• test_restart_endpoint_after_switch_wal: release-arm64

Code coverage* (full report)

• functions: 31.3% (7486 of 23881 functions)
• lines: 49.6% (60088 of 121224 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
12a5727 at 2024-10-01T15:48:04.993Z :recycle:}