feat(pageserver): store reldirv2 migration in key

[skyzh]

Problem

• we cannot use dbdir unfortunately.
• one more read, but we can cache it (in next few patches).

Summary of changes

• index_part.json is no longer used for reldir migration status, will clean up in the future.
• we store the migration status in a key in the reldir sparse keyspace.
• new rel_size_v1_access_disabled field to completely disable v1 writes and reads.
• adjust test cases accordingly.
• enable reldirv2 in tests by default.

[github-actions]

9053 tests run: 8356 passed, 47 failed, 650 skipped (full report)

---

Failures on Postgres 17

• test_fully_custom_config: release-x86-64-without-lfc, release-x86-64-with-lfc, debug-x86-64-without-lfc, release-arm64-with-lfc, release-arm64-without-lfc
• test_image_consistent_lsn: release-x86-64-without-lfc, release-x86-64-with-lfc, debug-x86-64-without-lfc, release-arm64-with-lfc
• test_pg_regress[v2-None]: release-x86-64-with-lfc, release-x86-64-without-lfc, release-arm64-without-lfc, debug-x86-64-without-lfc, release-arm64-with-lfc
• test_pg_regress[v2-4]: release-x86-64-without-lfc, release-x86-64-with-lfc, release-arm64-with-lfc, release-arm64-without-lfc, debug-x86-64-without-lfc
• test_sql_regress[v1-4]: debug-x86-64-without-lfc
• test_sql_regress[v2-4]: debug-x86-64-without-lfc
• test_sql_regress[v1-None]: debug-x86-64-without-lfc
• test_sql_regress[v2-None]: debug-x86-64-without-lfc

Failures on Postgres 16

• test_fully_custom_config: release-x86-64-with-lfc, release-arm64-with-lfc
• test_image_consistent_lsn: release-x86-64-with-lfc, release-arm64-with-lfc
• test_pg_regress[v2-None]: release-x86-64-with-lfc, release-arm64-with-lfc
• test_pg_regress[v2-4]: release-x86-64-with-lfc, release-arm64-with-lfc

Failures on Postgres 15

• test_fully_custom_config: release-x86-64-with-lfc, release-arm64-with-lfc
• test_image_consistent_lsn: release-x86-64-with-lfc, release-arm64-with-lfc
• test_pg_regress[v2-None]: release-x86-64-with-lfc, release-arm64-with-lfc
• test_pg_regress[v2-4]: release-x86-64-with-lfc, release-arm64-with-lfc

Failures on Postgres 14

• test_fully_custom_config: release-x86-64-with-lfc, release-arm64-with-lfc
• test_image_consistent_lsn: release-x86-64-with-lfc, release-arm64-with-lfc
• test_pg_regress[v2-4]: release-x86-64-with-lfc, release-arm64-with-lfc
• test_pg_regress[v2-None]: release-x86-64-with-lfc, release-arm64-with-lfc

# Run all failed tests locally:
scripts/pytest -vv -n $(nproc) -k "test_fully_custom_config[release-pg14] or test_fully_custom_config[release-pg14] or test_image_consistent_lsn[release-pg14] or test_image_consistent_lsn[release-pg14] or test_pg_regress[release-pg14-v2-4] or test_pg_regress[release-pg14-v2-4] or test_pg_regress[release-pg14-v2-None] or test_pg_regress[release-pg14-v2-None] or test_fully_custom_config[release-pg15] or test_fully_custom_config[release-pg15] or test_image_consistent_lsn[release-pg15] or test_image_consistent_lsn[release-pg15] or test_pg_regress[release-pg15-v2-None] or test_pg_regress[release-pg15-v2-None] or test_pg_regress[release-pg15-v2-4] or test_pg_regress[release-pg15-v2-4] or test_fully_custom_config[release-pg16] or test_fully_custom_config[release-pg16] or test_image_consistent_lsn[release-pg16] or test_image_consistent_lsn[release-pg16] or test_pg_regress[release-pg16-v2-None] or test_pg_regress[release-pg16-v2-None] or test_pg_regress[release-pg16-v2-4] or test_pg_regress[release-pg16-v2-4] or test_fully_custom_config[release-pg17] or test_fully_custom_config[release-pg17] or test_fully_custom_config[debug-pg17] or test_fully_custom_config[release-pg17] or test_fully_custom_config[release-pg17] or test_image_consistent_lsn[release-pg17] or test_image_consistent_lsn[release-pg17] or test_image_consistent_lsn[debug-pg17] or test_image_consistent_lsn[release-pg17] or test_pg_regress[release-pg17-v2-None] or test_pg_regress[release-pg17-v2-None] or test_pg_regress[release-pg17-v2-None] or test_pg_regress[debug-pg17-v2-None] or test_pg_regress[release-pg17-v2-None] or test_pg_regress[release-pg17-v2-4] or test_pg_regress[release-pg17-v2-4] or test_pg_regress[release-pg17-v2-4] or test_pg_regress[release-pg17-v2-4] or test_pg_regress[debug-pg17-v2-4] or test_sql_regress[debug-pg17-v1-4] or test_sql_regress[debug-pg17-v2-4] or test_sql_regress[debug-pg17-v1-None] or test_sql_regress[debug-pg17-v2-None]"

Flaky tests (10)

Postgres 17

• test_sql_regress[v2-4]: release-arm64-with-lfc, release-arm64-without-lfc
• test_sql_regress[v2-None]: release-arm64-with-lfc, release-arm64-without-lfc

Postgres 16

• test_sql_regress[v2-None]: release-arm64-with-lfc
• test_sql_regress[v2-4]: release-arm64-with-lfc

Postgres 15

• test_sql_regress[v2-4]: release-arm64-with-lfc
• test_sql_regress[v2-None]: release-arm64-with-lfc

Postgres 14

• test_sql_regress[v2-4]: release-arm64-with-lfc
• test_sql_regress[v2-None]: release-arm64-with-lfc

Test coverage report is not available

_{The comment gets automatically updated with the latest test results
13b84d8 at 2025-07-28T21:00:32.771Z :recycle:}

[skyzh]

closing in favor of #12758