Excimer causes memory exhaustion to trigger a segfault

Typical memory exhaustion errors are causing PHP to segfault, instead of fatal errorring. This kills the worker (and any shared memory it may be storing) and causes un-traceable user errors, significantly complicating debugging.

I also believe that this is the root cause of the problems with `load-scripts.php` we were seeing which we attributed to the JIT - they are actually out-of-memory issues which then become segfaults due to this bug as well as https://github.com/WordPress/gutenberg/issues/54294

I've traced this down specifically to our use of Excimer, likely in X-Ray.

Minimal reproduction:
1. Run local server the usual way
2. Save the following into a PHP file in `content/mu-plugins/`:
```

Acceptance criteria:

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