Fix build on JDK 21+, resolves #1146

[superaxander]

Files were not being generated leading to the missing packages in #1146

It seems on newer JDKs there is no $ after Lambda so that caused our name matching to fail.

Example of what a class name looks like now:

scala.meta.internal.prettyprinters.TreeSyntax$SyntaxInstances$$Lambda/0x00007f00eac376f8

[superaxander]

I was wondering why the ??? didn't cause an exception which would've failed the generation phase of the build, but it happens inside a Using where the resulting Try is ignored

[pieter-bos]

Yeah I've just misunderstood how Using works, likely all uses of Using should be replaced with Using.resource. Like I mentioned recently these would have been catched by -Wvalue-discard, but it has a good number of false positives for our code.