tests: use high IO concurrency in test_pgdata_import_smoke, use effective_io_concurrency=2 in tests by default

[jcsp]

Problem

test_pgdata_import_smoke writes two gigabytes of pages and then reads them back serially. This is CPU bottlenecked and results in a long runtime, and sensitivity to CPU load from other tests on the same machine.

Closes: #10071

Summary of changes

• Use effective_io_concurrency=32 when doing sequential scans through 2GiB of pages in test_pgdata_import_smoke. This is a ~10x runtime decrease in the parts of the test that do sequential scans.
• Also set effective_io_concurrency=2 for tests, as I noticed while debugging that we were doing all getpage requests serially, which is bad for checking the stability of the batching code.

[github-actions]

7095 tests run: 6798 passed, 0 failed, 297 skipped (full report)

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Flaky tests (3)

Postgres 17

• test_physical_replication_config_mismatch_too_many_known_xids: debug-x86-64

Postgres 16

• test_lr_with_slow_safekeeper: release-arm64

Postgres 14

• test_gc_blocking_by_timeline[True]: release-arm64

Code coverage* (full report)

• functions: 31.2% (8392 of 26865 functions)
• lines: 48.0% (66633 of 138945 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
5ae4824 at 2024-12-19T10:54:30.808Z :recycle:}