failing feature (bug) for nested step backtraces
Update nested_steps.feature

This is what I think the nested steps backtrace should ideally look like.

This matches the way Ruby backtraces work: they show the line where the call happened, rather than the line of the containing method.
Don't filter the whole backtrace too early.
Delete remaining backtrace if there are no more lines to modify
Include nested steps in output of legacy features.
Filter jruby core lines from backtraces by default on jruby
Migrate from legacy_features/call_steps_from_stepdefs to features/nested_steps

This gives the same coverage as the old feature without relying on
exceptions/backtraces.