pageserver: apply shard filtering to blocks ingested during initdb

[jcsp]

Problem

Ingest filtering wasn't being applied to timeline creations, so a timeline created on a sharded tenant would use 20MB+ on each shard (each shard got a full copy). This didn't break anything, but is inefficient and leaves the system in a harder-to-validate state where shards initially have some data that they will eventually drop during compaction.

Closes: #6649

Summary of changes

• in import_rel, filter block-by-block with is_key_local
• During test_sharding_smoke, check that per-shard physical sizes are as expected
• Also extend the test to check deletion works as expected (this was an outstanding tech debt task)

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

[github-actions]

2796 tests run: 2672 passed, 0 failed, 124 skipped (full report)

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Flaky tests (1)

Postgres 14

• test_storcon_cli: debug

Code coverage* (full report)

• functions: 27.9% (6382 of 22848 functions)
• lines: 46.8% (44999 of 96058 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
c83b04a at 2024-04-05T08:58:22.912Z :recycle:}