Disable prepareStackTrace while we're generating stacks (#18708)

This could be used to do custom formatting of the stack trace in a way
that isn't compatible with how we use it. So we disable it while we use
it.

In theory we could call this ourselves with the result of our stack.
It would be a lot of extra production code though. My personal opinion
is that this should always be done server side instead of on the client.

We could expose a custom parser that converts it and passes it through
prepareStackTrace as structured data. That way it's external and doesn't
have to be built-in to React.