test straxen for coverage and backward compatibility

[JoranAngevaare]

• We could increase coverage by running straxen tests on coveralls
• We could check if changes in a PR would cause issues for running straxen. A fail here would mean we introduce breaking changes. We could either avoid doing that or allow it and fix it on straxens master

In this PR, we don't use any of straxens secrets, so we don't have database access

[coveralls]

Pull Request Test Coverage Report for Build 1736061280

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+2.9%) to 88.807%

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Totals
Change from base Build 1696976384:	2.9%
Covered Lines:	4570
Relevant Lines:	5146

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💛 - Coveralls

[WenzDaniel]

Nice idea, I like it. Is our testing with coveralls limited? In that case we might only run it under certain conditions. E.g. making a new release.

[JoranAngevaare]

@WenzDaniel , no there is no time constrain. It's only the (possible) annoyance of having to iterate between strax <-> straxen. Could be a good motivation to make sure things are backward compatible at least one release but can also see this being annoying sometimes.

[WenzDaniel]

In that case I would propose to just give it a try.