tests: refine how compat snapshot is generated

[jcsp]

Problem

I noticed in #9537 that tests which work with compat snapshots were writing several hundred MB of data, which isn't really necessary.

Also, the snapshots are large but don't have the proper variety of storage format features, e.g. they could just have L0 deltas.

Summary of changes

• Use smaller scale factor and runtime to generate less data
• Configure a small layer size and use force image layer generation so that our output contains L1 deltas and image layers, and has a decent number of entries in the layer map

[bayandin]

Nice, thanks!

[github-actions]

7293 tests run: 6928 passed, 0 failed, 365 skipped (full report)

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Flaky tests (1)

Postgres 15

• test_parallel_copy: release-arm64

Code coverage* (full report)

• functions: 32.7% (8044 of 24618 functions)
• lines: 47.8% (66829 of 139908 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
90b2906 at 2025-01-10T13:45:00.975Z :recycle:}