Expose the number of StackOverflowErrors encountered by JVM

src/hotspot/share/utilities/exceptions.cpp
A variable "_stack_overflow_errors" tracks StackOverflowErrors.

Knowing whether a JVM has experienced StackOverflowError(s) is an important data point in debugging lost (java.util.concurrent) Locks, hangs etc. There's a JFR option but recordings at time of Error may not be possible.

Exposing "_stack_overflow_errors" via a hotspot/VM MXBean seems like something that could be straightforward to achieve and benefit cases where such data is required.