Simplify scanning compute logs in tests

[hlinnaka]

Implement LogUtils in the Endpoint fixture class, so that the "log_contains" function can be used on compute logs too.

Per discussion at:
#7288 (comment)

[github-actions]

3192 tests run: 3053 passed, 0 failed, 139 skipped (full report)

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Flaky tests (1)

Postgres 15

• test_synthetic_size_while_deleting: debug

Code coverage* (full report)

• functions: 31.5% (6598 of 20963 functions)
• lines: 48.4% (51066 of 105401 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
263da3f at 2024-06-10T12:23:47.797Z :recycle:}