Starting with PhpStorm 2023.3 there are new rules for multithreading that phpunit_codecoverage does not comply with. See https://plugins.jetbrains.com/docs/intellij/general-threading-rules.html
For a workaround I found the plugin and removed it and PhpStorm was able to start up again. Leaving a note here in case others encounter an issue where PhpStorm won't start up, and this plugin is mentioned in the stack trace.