[25] JavaSearchBugs16Tests.testAIOOBEForRecordClassGh790() throws AssertionError

Running the given test on JDK 25 raises
`java.lang.AssertionError: PlainPackageBinding cannot be parent of split package sun.text.spi (from java.base, java.base)`

This happens when we try to resolve a PossibleMatch for `module-info.class [in [in ]]`

At that point we have both a SourceModuleBinding and a BinaryModuleBinding for java.base, producing a pseudo split package.

I'm not sure if we can accept this schizophrenia of a module, but then we probably cannot avoid the BinaryModuleBinding of the premordial module, nor can we use it for reference search, so we need the source variant, too :-/