[jvm] duplicated filename creates exceptions when updating snapshot

There is a possible issue that I encountered with duplicated file names of tests. (in different packages). The assertion was marked for overwrite with `toBe_TODO()` and the following exception was thrown:
```
[com.diffplug.selfie.junit5.SelfieTestExecutionListener] threw exception for method: testPlanExecutionFinished(org.junit.platform.launcher.TestPlan@65b49da9) java.lang.AssertionError: Expected to find inline assertion on line ...
```
With some debugging i found that there was a file with a identical name red with different content instead of the correct one, before the exception was thrown.

Also I'm not sure if this a known limitation or a bug