support JUnit output format

[GiladShoham]

Many CI tools can parse JUnit output format and display the results in a more user-friendly UI. Adding support for JUnit output would greatly improve the ability to understand and analyze issues when running oxlint in CI environments.

[nrayburn-tech]

https://github.com/testmoapp/junitxml contains some info on the file format. Not sure if there's a more official spec somewhere, but I couldn't find one.

Something for the Oxc team to consider might be a way for users to provide their own output format. Would probably require exposing the raw lint results to a JavaScript file, so that the user could build their output format in JavaScript.

[GiladShoham]

@nrayburn-tech
This is connected to #4868
if we will have better json output we can build the junit format from it