In terms of memory allocations, this reduces the overall memory
allocations of creating a location by an order of magnitude in
Java 9, and as compared to Java 8.

The implementation is somewhat involved due to these desires:

- Minimize the amount of work done if the Location is never used. This
  is done by not converting the StackFrame into a StackTraceElement,
  instead wrapping in an intermediate state. The StackTraceElement conversion
  will only occur (internally) if the .getFileName() method is called.
- Ensure the implementation is still Serializable. This is ensured with
  a .writeReplace method.
- Minimize the number of allocations, which is basically an exercise in
  lambda caching.
- Ensuring the old mechanism still works on Java 8.

Presently on Java 9+, on a stack depth of 1000 the old mechanism will allocate
40kB of RAM per call. The new one will allocate 1.5kB of RAM per call,
which is a huge improvement.

This is still sadly not the 'close-to-no-overhead' solution I was
looking for. I therefore also added a system property that can be used
to fully disable Location creation. I'm aware that this is likely not
the right approach given Mockito has plugins and settings - mostly
looking for guidance here given I'm not sure what would be idiomatic
here.