Investigate com.sun.tools.classfile usage

JDK 25+ doesn't have the `com.sun.tools.classfile` package anymore (since it got replaced by the public [classfile-api](https://openjdk.org/jeps/484)), compare:
- https://github.com/search?q=repo%3Aopenjdk%2Fjdk24u+com.sun.tools.classfile&type=code
- https://github.com/search?q=repo%3Aopenjdk%2Fjdk25u+com.sun.tools.classfile&type=code

symptom: Noticed this while observing startup warnings:
```
WARNING: package com.sun.tools.classfile not in jdk.jdeps
```

so, why does it not explode at runtime? nb-javac ships it. Where does it get it from when it is lo longer in the JDK? It is copied from nb-javac 21 (!) producing a frankenstein javac:

https://github.com/JaroslavTulach/nb-javac/blob/50889546cfec421fbfc85158332cede5522d3af2/make/langtools/netbeans/nb-javac/build.xml#L202-L208

https://github.com/JaroslavTulach/nb-javac/blob/50889546cfec421fbfc85158332cede5522d3af2/make/langtools/netbeans/nb-javac/build.xml#L313

https://github.com/JaroslavTulach/nb-javac/commit/2781c00716f60f2510d29f76e236fb62b19f07eb

NB usage is only via [classfile/CodeGenerator](https://github.com/apache/netbeans/blob/master/java/java.source/src/org/netbeans/modules/java/classfile/CodeGenerator.java) and some Strings:
https://github.com/search?q=repo%3Aapache%2Fnetbeans%20com.sun.tools.classfile&type=code

Would be good to try to remove usage within NB and remove it from nb-javac too or switch to JEP 484 somehow (hopefully without having to ship it with nb-javac since that would likely no longer be possible for several reasons).