Improve performance of `BasicStreamReader.readTextSecondary()` by using bulk-copy

While experimenting with possible performance gains using the Java Vector API (yes, there are some 😉) I came across a rather simple and effective (~30% when microbenchmarking a specific use-case) performance optimization for `BasicStreamReader.readTextSecondary()` that would also fly with Java 8. It is explained [in detail in the PR](https://github.com/winfriedgerlach/woodstox/blob/e62aebaf6605aadc39360f32ef3b77aebd51f367/benchmark/README.md).

I'll post a draft pull request here with all the heavy lifting done by Claude Code, and I don't expect you to merge this as is. But the code change is small enough to be quickly reviewed and adapted by humans.