product webservice "time" parameter does not work with open intervals
Time parameter currently only matches products that specify `starttime` and `endtime` parameters:
https://code.usgs.gov/ghsc/hazdev/earthquake-event-ws/-/blob/master/src/lib/classes/pdl/ProductIndex.class.php#L1859-1863
- [ ] allow `starttime`/`endtime` to be undefined as an open time interval, essentially:
```
(product.starttime IS NULL or product.starttime <= time)
AND (product.endtime IS NULL or product.endtime >= time)
```
issue