chore: fix clippy lints from nightly-2025-03-16

[conradludgate]

I like to run nightly clippy every so often to make our future rust upgrades easier. Some notable changes:

• Prefer next_back() over last(). Generic iterators will implement last() to run forward through the iterator until the end.

• Prefer io::Error::other().

• Use implicit returns

One case where I haven't dealt with the issues is the now more-sensitive "large enum variant" lint. I chose not to take any decisions around it here, and simply marked them as allow for now.

[github-actions]

8019 tests run: 7635 passed, 0 failed, 384 skipped (full report)

---

Flaky tests (6)

Postgres 16

• test_lfc_working_set_approximation: release-arm64-with-lfc
• test_sql_regress[v2-4]: release-arm64-with-lfc

Postgres 15

• test_compute_pageserver_hung_connections: release-arm64-with-lfc
• test_compute_pageserver_statement_timeout: release-arm64-with-lfc
• test_location_conf_churn[3]: release-arm64-with-lfc

Postgres 14

• test_compute_pageserver_hung_connections: release-x86-64-with-lfc

Code coverage* (full report)

• functions: 32.3% (8734 of 27036 functions)
• lines: 48.5% (75332 of 155198 lines)

* collected from Rust tests only

---

_{The comment gets automatically updated with the latest test results
c6372b1 at 2025-03-31T16:25:25.113Z :recycle:}

[tristan957]

Looks like you will need to force push. The cloud repo commit that got picked up is broken.