Improve worker runtime + teardown

[maidh91]

• Allow custom runtime

  • see test: https://github.com/holepunchto/pear/pull/415

• Use teardown for pipe end/close handler

  • note that If the process is exited explicitly, such as by calling Bare.exit() or as the result of an uncaught exception, the beforeExit event will not be emitted.
  • see https://github.com/holepunchto/bare/blob/main/README.md#bareonbeforeexit-code
  • see test: https://github.com/holepunchto/pear/pull/416 => this new way ensures that teardown handlers run first before ending pipe or exiting the process