Try building images using Debian 12 "Bookworm" for PG17

[MMeent]

This increases the support window of the OS used for PG17 by 2 years compared to the previous usage of Debian 11 "Bullseye".

Problem

Maintaining Debian 11 support for the full lifetime of our PG17 support is unlikely to be productive. Pre-emptively deploy PG17 on Debian 12, which should give us at least 2 more years of headroom vs Debian 11.

Summary of changes

Building the compute image is now parameterized with DEBIAN_FLAVOR, or the Debian docker base image used. For older versions that's still 'bullseye-slim', but for PG17 we now have 'bookworm-slim'.

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]

5090 tests run: 4926 passed, 0 failed, 164 skipped (full report)

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Flaky tests (9)

Postgres 17

• test_pageserver_compaction_smoke: release-arm64
• test_isolation[None]: debug-x86-64
• test_readonly_node_gc: debug-x86-64
• test_subscriber_restart: release-x86-64, debug-x86-64

Postgres 16

• test_subscriber_restart: release-x86-64

Postgres 15

• test_sharding_split_smoke: release-arm64

Postgres 14

• test_physical_replication: release-x86-64
• test_storage_controller_compute_hook: release-x86-64

Code coverage* (full report)

• functions: 32.1% (7474 of 23255 functions)
• lines: 49.9% (60224 of 120574 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
b667b80 at 2024-09-24T23:45:54.139Z :recycle:}