[pyroscope.java] Metrics on JFR files written to disk to help measure disk usage

[swar8080]

Request

Some metrics on how many bytes of JFR files are written to disk by pyroscope.java would help adjust disk size and give us confidence to more broadly enable continuous profiling

A nice to have would be a distribution of file sizes so we can estimate the "worst case" when applications with larger JFR files are unluckily scheduled on the same kubernetes node

Use case

Similar to #1960, we are being cautious about using up to much disk space

[github-actions]

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