Check if relation has storage in calculate_relation_size

[knizhnik]

Problem

Parent of partitioned table has no storage, it relfilelocator is zero.
It cab be incorrectly hashed and produce wrong results.

See neondatabase/postgres#518

Summary of changes

This problem is already addressed in pg17.
Add the same check for all other PG versions.

Postgres PRs:
neondatabase/postgres#566
neondatabase/postgres#565
neondatabase/postgres#564

[github-actions]

7403 tests run: 7015 passed, 0 failed, 388 skipped (full report)

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Flaky tests (7)

Postgres 17

• test_pageserver_gc_compaction_idempotent[after_restart]: release-arm64-with-lfc
• test_metrics_normal_work: release-x86-64-without-lfc, release-x86-64-with-lfc

Postgres 16

• test_metrics_normal_work: release-arm64-with-lfc

Postgres 15

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

Postgres 14

• test_branch_creation_before_gc: release-arm64-with-lfc
• test_timeline_copy[100000]: release-arm64-with-lfc

Code coverage* (full report)

• functions: 33.5% (8498 of 25347 functions)
• lines: 49.3% (71482 of 144985 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
973beb4 at 2025-01-24T11:37:24.475Z :recycle:}

[MMeent]

Looks like it needs some applied conflict resolution w.r.t. /vendor, but apart from that LGTM.