Photon: filter attachment_url_to_postid() to support Photon CDN URLs

### Impacted plugin

Jetpack

### Steps to Reproduce

1. Install Jetpack.
2. Turn on the Photon image CDN, (Jetpack > Settings > Performance > Performance & Speed and turn on the "Enable site accelerator" and "Speed up image load times" toggles).
3. Pass the CDN URL of any image in the media gallery to WordPress's [`attachment_url_to_postid()`](https://developer.wordpress.org/reference/functions/attachment_url_to_postid/) function.
4. Inspect the return value from the function. It should be an integer post ID, but it'll be zero.

### A clear and concise description of what you expected to happen.

I expect the post ID of the attachment to be returned by `attachment_url_to_postid()` even with Photon active.

### What actually happened

`attachment_url_to_postid()` returns a zero, which means it failed to look up the post ID of the image.

### Other information

This bug makes sense, because `attachment_url_to_postid()` queries the database for the URL that was passed in, and the CDN URL is not in the database.

However, there is a `attachment_url_to_postid` filter, and I expect that Jetpack would be a good WordPress citizen and, when Photon is on, use that filter to extract the original from the CDN URL and look up the post ID based on the original URL.

### Operating System

macOS, Linux

### OS Version

Confirmed on both Linux webserver and macOS localhost.

### Browser

Other / Not applicable

### Browser Version(s)

Not a browser problem.

Start by searching Jetpack's Photon CDN URL handling and WordPress's attachment_url_to_postid filter. Reproduce the failure with a CDN image URL, then verify that the filter allows the attachment post ID to be found from the original image URL.

Written by the indexing model from the issue text.