ISBAT parse ICS objects, or remove feature from Events block

### Describe the bug:

Events block is using an external ICS calendar parser. Presently, the parser is not working any longer and is either throwing an error or is silently failing without error. The issue is confirmed to be present in both WP 6.2.2 as well as WP 6.3.

We should consider completely deprecating the feature now. Actually, ideally we move this into a core block completely and deprecate the whole Events block.

### To reproduce:

1. Add Events block.
2. Enable the external ICS calendar.
3. Try this one. 'https://calendar.google.com/calendar/ical/8hohgb8qv19fgvjbbkcehe0ce0%40group.calendar.google.com/public/basic.ics'
4. Either see error or silent fail depending on local conditions.

### Expected behavior:

Expect ICS calendars to parse.

### Screenshots:

Silent fail in prod, and apparently in some CI instances.

Fail seen in 7.4, and running 8.0 locally with wp-env.

```js
api-fetch.js?ver=c6922e5e289e31508e9e:727 GET http://localhost:8888/index.php?rest_route=%2Fwp%2Fv2%2Fblock-renderer%2Fcoblocks%2Fevents&context=edit&attributes%5BexternalCalendarUrl%5D=https%3A%2F%2Fcalendar.google.com%2Fcalendar%2Fical%2F8hohgb8qv19fgvjbbkcehe0ce0%2540group.calendar.google.com%2Fpublic%2Fbasic.ics&attributes%5BeventsRange%5D=all&attributes%5BeventsToShow%5D=5&attributes%5BshowCarousel%5D=true&post_id=4&_locale=user 500 (Internal Server Error)
```

### Isolating the problem:

- [x] This bug happens with no other plugins activated
- [x] This bug happens with a default WordPress theme active
- [x] This bug happens **without** the Gutenberg plugin active
- [x] I can reproduce this bug consistently using the steps above

### WordPress version:

6.2.2 & 6.3

### Gutenberg version:

N/A