Support develocity in JUnitXml reporting.

[ZacSweers]

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Resolves #384 by supporting both develocity and GE. Also modernizes the report file handling a little.

[ZacSweers]

I think CI is too old. This passes for me locally

[ritesh-singh]

Thanks @ZacSweers for opening the PR. Right on time 😆 I was in the process of creating one!!

[runningcode]

Thanks for the PR. Could you please run :fladle-plugin:formatKotlinMain to fix the failing build?

[ZacSweers]

Done 👍