tests: use fewer pageservers in test_sharding_split_smoke

[jcsp]

Problem

This test uses a gratuitous number of pageservers (16). This works fine when there are plenty of system resources, but causes issues on test runners that have limited resources and run many tests concurrently.

Related: #9802

Summary of changes

• Split from 2 shards to 4, instead of 4 to 8
• Don't give every shard a separate pageserver, let two locations share each pageserver.

Net result is 4 pageservers instead of 16

[github-actions]

5526 tests run: 5300 passed, 0 failed, 226 skipped (full report)

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Flaky tests (1)

Postgres 15

• test_pull_timeline[True]: release-x86-64

Code coverage* (full report)

• functions: 31.4% (7941 of 25300 functions)
• lines: 49.3% (63013 of 127730 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
0b6c293 at 2024-11-20T13:54:19.434Z :recycle:}