[13.x] Allow lifecycle and output callbacks on Schedule::group() (#60133)

Adds support for `before`, `after`, `then`, `onSuccess`, `onFailure` (and
their `*WithOutput` / `ping*` / `*OutputTo` variants) when chaining before
`Schedule::group()`. Previously these methods reached `Schedule::__call`,
which had no way to defer Event-only methods, and threw
`BadMethodCallException`.

`PendingEventAttributes::__call` now also recognizes a fixed list of
deferred Event methods (in addition to user-registered Event macros) and
records them to be replayed on every event in the group via
`mergeAttributes`. Per-event callbacks declared inside the group closure
still apply on top, after the group-level ones.