Export db size metrics for 10 user databases

[zaynetro]

Problem

One database is too limiting. We have agreed to raise this limit to 10.

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]

3132 tests run: 3005 passed, 0 failed, 127 skipped (full report)

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Flaky tests (3)

Postgres 15

• test_vm_bit_clear_on_heap_lock: debug

Postgres 14

• test_timeline_deletion_with_files_stuck_in_upload_queue: debug
• test_fixture_restart: release

Code coverage* (full report)

• functions: 31.4% (6450 of 20544 functions)
• lines: 48.3% (49865 of 103260 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
e599b60 at 2024-05-23T09:36:49.821Z :recycle:}