Tests: redirect log to test output

[majocha]

Description

In the test suite log was originally an alias for printfn:

    let log format = printfn format

My previous changes made its output to essentially go nowhere. There are however many log calls in the tests. As it is essentially printfn, it should print to the output of the respective test case, just like printfn.

Fixes:
result of

can be seen in test output:

[github-actions]

✅ No release notes required

[psfinaki]

Nice, thanks a lot!

[psfinaki]

/azp run

[psfinaki]

/azp run

[azure-pipelines]

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