Paging support for threads

Similarly to paging support for stackTrace, it would be quite useful if DAP provided paging support for threads.

We came across this with Go goroutines - lightweight virtual threads, where loading all of them at once is quite costly and can even freeze the system (e.g. https://github.com/golang/vscode-go/issues/129). A concurrent Go application can have hundreds of thousands of goroutines, maybe even millions. It is questionable how much interactive debugging happens at that scale, but paging is helpful even if there are only hundreds of threads, a possibility for other languages as well. This would make it possible for editors to limit the amount of threads to display to something manageable and to load more on demand, perhaps with a feature to look up a specific thread by some kind of id/label or condition.