Support export to JFR

#### Is your feature request related to a problem? Please describe.

Some external analysis tools, like the Firefox Profiler or Perfetto, don't support the pprof format. However, they do support JFR (perhaps after some [conversion steps](https://profilerpedia.markhansen.co.nz/formats/jfr/#converts-to-transitive)).

#### Describe the solution you'd like

Since the Java SDK already uploads continuous profiles to Pyroscope in JFR format, it would be very useful to be able to dump this data directly from the UI.

#### Describe alternatives you've considered

There are analysis UIs that support pprof natively, such as Speedscope, but they lack Firefox Profiler features.