feat: add `min` param and `timedelta` support to `wait_exponential_jitter` (#628)

`wait_exponential` already supports `min` and `timedelta` for min/max.
`wait_exponential_jitter` lacked both, which was an inconsistency users
asked for in #426.

- Accept `timedelta` for `max`, `jitter`, and `min` parameters
- Add `min` parameter to set a minimum wait time floor
- Convert all time parameters via `_utils.to_seconds()` in `__init__`


Change-Id: Ic02ae68b863cc0d1cd5a3b7874006c193c0c14a8

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>